On Friday, Palo Alto Networks released an advisory warning users of Palo Alto's Global Protect product of a vulnerability that has been exploited since March [1].
Volexity discovered the vulnerability after one of its customers was compromised [2]. The vulnerability allows for arbitrary code execution. As of today, an exploit has been made public on GitHub. I have not had a chance to test if the exploit is real. I doubt it is real because I hope Palo Alto did apply a bit more due diligence to its products than let a trivial to exploit vulnerability slip in. On the other hand, we have seen similar vulnerabilities from security tool vendors before.
Assume Compromise
According to Volexity, exploit attempts for this vulnerability were observed as early as March 26th. A simple PoC is now publicly available.
Workarounds
GlobalProtect is only vulnerable if telemetry is enabled. Telemetry is enabled by default, but as a "quick fix", you may want to disable telemetry. Palo Alto Threat Prevention subscribers can enable Threat ID 95187 to block the exploit.
Patch
A patch should be available soon (it is not available as I am writing this). Check with Palo Alto for updates.
The SIFT Workstation[1] is a well-known Linux distribution oriented to forensics and incident response tasks. It is used in many SANS training as the default platform. This is also my preferred solution for my day-to-day DFIR activities. The distribution is available as a virtual machine but you can install it on top of a classic Ubuntu system. Today, everything is virtualized and most DFIR activities can be performed remotely with the provided VM but… sometimes you still need a way to perform local investigations against a physical computer. That's why I always carry a USB stick with me. Before I was using Kali which provides a standard solution.
We live in a dynamic age, especially with the increasing awareness and popularity of Artificial Intelligence (AI) systems being explored by users and organizations alike. I was recently quizzed by a junior researcher on how AI systems came about and realized I could not answer that query immediately. I had a rough idea of what led to the current generative and large language models. Still, I had a very fuzzy understanding of what transpired before them, besides being confident that neural networks were involved. Unsatisfied with the lack of appreciation of how AI systems evolved, I decided to explore how AI systems were conceptualized and developed to the current state, sharing what I learnt in this diary. However, knowing only how to use them but being unable to ensure their trustworthiness (especially if organizations want to use these systems for increasingly critical business activities) could expose organizations to a much higher risk than what senior leadership could accept. As such, I will also suggest some approaches (technical, governance, and philosophical) to ensure the trustworthiness of these AI systems.
This update covers a total of 157 vulnerabilities. Seven of these vulnerabilities are Chromium vulnerabilities affecting Microsoft's Edge browser. However, only three of these vulnerabilities are considered critical. One of the vulnerabilities had already been disclosed and exploited.
Ever since the LockBit source code leak back in mid-June 2022 [1], it is not surprising that newer ransomware groups have chosen to adopt a large amount of the LockBit code base into their own, given the success and efficiency that LockBit is notorious for. One of the more clear-cut spinoffs from LockBit, is Darkrace, a ransomware group that popped up mid-June 2023 [2], with samples that closely resembled binaries from the leaked LockBit builder, and followed a similar deployment routine. Unfortunately, Darkrace dropped off the radar after the administrators behind the LockBit clone decided to shut down their leak site.
It is unsurprising that, 8 months after the appearance and subsequent disappearance of the Darkrace group, a new group who call themselves DoNex [3], have appeared in their place, utilizing samples that closely resemble those previously used by the Darkrace group, and LockBit by proxy.
Analysis
Dropping the DoNex sample [4] in "Detect It Easy" (DIE) [5], we can see the binary does not appear to be packed, is 32-bit, and compiled with Microsoft's Visual C/C++ compiler.
Figure 1: Binary Opened in DIE
Opening the sample in Binary Ninja [6], and switching to the "Triage Summary" view, we can standard libraries being imported, and sections with nothing special going on.
Figure 2: Binary Ninja Triage Summary
Switching back to the disassembly view, and going to the entry point, we can follow execution to the actual main function.
Figure 3: Entry Point
Figure 4: Call to Main Function
Once the application is launched, the main function starts by getting a handle to the attached console window with "FindWindowA", and setting the visibility to hidden by calling "ShowWindow" and passing "SW_HIDE" as a parameter.
Figure 5: Main Function
Following execution into the next function called (renamed to "doInit"), we can see a mutex check to ensure only one instance of the application will run and encrypt files.
Figure 6: Mutex Check
The next notable function called (renamed to "checkPrivs"), is an attempt to fetch the access token from the current thread by using "GetCurrentThread" with "OpenThreadToken", and in cases where this operation fails, "GetCurrentProcess" is used with "OpenProcessToken" to obtain the access token from the application process, instead of the current thread.
Figure 7: Get Access Token
Using the access token handle, "GetTokenInformation" is called to identify the user account information tied to the token, most notably the SID.
Figure 8: Get Token Info
The user account info will be used to check for administrative rights, so a SID for the administrators group is allocated and initialized.
Figure 9: Admin SID Create
Now with the SID for the administrators group, "EqualSid" is called to compare the SID from derived from the token information against the newly initialized SID for the administrators group
Figure 10: Admin Context Check
Returning back to the main function, next "GetModuleHandleA" is used to open a handle to "kernel32.dll" module, and "GetProcAddress" is called using that handle to resolve the address of the "IsWow64Process" function.
Figure 11: Dynamic Address Resolution
Using the now resolved "IsWow64Process" function, the handle of the current process is passed and used to determine if "Windows on Windows 64" (WOW64 is essentially an x86 emulator) is being used to run the application. WOW64 file system redirection is then disabled if the application is either running under 32-bit Windows, or if it is running under WOW64 on 64-bit Windows. Disabling redirection allows 32-bit applications running under WOW to access 64-bit versions of system files in the System32 directory, instead of being redirected to the 32-bit directory counterpart, SysWOW64.
Figure 12: WOW FS Redirection Check
From the main function we follow another call to the function (renamed to "doCryptoSetup") responsible for acquiring the cryptographic context needed for the application to actually encrypt device files by calling, as the name implies "CryptAcquireContextA".
Figure 13: Acquire Crypot Context
With the cryptographic context setup, the following function (renamed to "setIcon") called, is used to drop an icon file named "icon.ico" to "C:ProgramData", and create keys in the device registry through use of "RegCreateKeyExA", and "RegSetValueExA", to set it as the default file icon for newly encrypted files.
Figure 14: Drop Icon File
Figure 15: Associate Icon with Extension
Figure 16: Set Default Icon in Registry
The final part of the initial setup process involves a call to "SHEmptyRecycleBinA", which as the name implies, empties the recycle bin, and since no drive was specified, it will affect all the device drives.
Figure 17: Wiping Recycle Bins
With the main pre-encryption setup complete, the encryption setup function (renamed to "mainEncryptSetup") which handles thread management, process termination, service control, drive & network share enumeration, file discovery & iteration, and encryption is called.
Figure 18: Encryption Setup Start
As part of the process termination and service control component, a connection to the service control manager on the local device is established through a call to "getServiceControl".
Figure 19: Service Control Connection
The first thread created during the encryption setup, is used to drop the process terminating batch file ("1.bat") [7] to the "ProgramData" directory. The second thread that is created, handles service manipulation, and executes if a valid handle to the service control manager is present.
Figure 20: Thread Creation
Called by the creation of the first thread, this function (renamed to "batRun") drops a looping batch file ("1.bat"), and executes it with "WinExec", which pings the localhost address, and uses "taskkill" to kill processes of common AV & EDR products and backup software.
Figure 21: Process Kill Batch
Called by the creation of the second thread, this function (renamed to "stopServices"), creates a connection to the service control manager through a call to "OpenSCManagerA", and has the capability to open handles to a service based on a service name, using "OpenServiceA", identify the service status with "QueryServiceStatusEx", identify any dependent services with "EnumDependentServicesA", and make modifications to the service, such as stopping it, with "ControlService".
Figure 22: Service Control Connection
Figure 23: Dependent Service Check
Figure 24: Control Service
After the previous two threads have finished, a list of valid storage drives connected to the device is enumerated with "GetLogicalDriveStringsW" and the drive type for each is queried using "GetDriveTypeW".
Figure 25: Storage Enumeration
The third and fourth threads will call functions "iterFiles" and "iterFilesCon", which handle discovering and iterating through the files on the previously queried drives. The fifth thread starts the actual file encryption process with a call to "startEncrypt".
Figure 26: Start Iterating Files
To start the process of iterating through files, the root path of the current targeted drive is identified using “getDriveRootPath”.
Figure 27: Get Drive Root
Files are then iterated through using “FindFirstFileW” and “FindNextFileW”, and checked against a file blacklist (“checkFileBlacklist”) to avoid encrypting critical system files, before being stored in a list to be used in the encryption process.
Figure 28: Start File Iteration
Figure 29: Compare Files to Blacklist
Figure 30: Release Handle and Finish Iteration
The encryption process starts with the execution of the “encryptJob” function, by the creation of the fifth thread
Figure 31: Start File Encryption Job
To ensure the encrypted data can be written to the target files, a Restart Manager session is created with “RmStartSession” and populated with the target files (resources) using “RmRegisterResources”, which are then collected by “RmGetList” and used to check if the target files are locked by any other processes, and if a lock exists, a handle is opened to the process, and the process is terminated, using “OpenProcess” and “TerminateProcess”. The target files are then finally encrypted.
Figure 32: Check File Locks
With the main encryption job finished, the ransom note “ReadMe” is dropped.
Figure 33: Dropping Ransom Note
Figure 34: Note Name with ID Placeholder
Figure 35: Note Written to Disk
With the main on-disk encryption job complete, available network shares are targeted next.
Figure 36: Target Network Shares
Network shares are enumerated through use of the Windows Networking API (“WNetOpenEnumW”), and connections are made to shares that are accessible by the current acting user account (“WNetEnumResourceW” and “WNetAddConnection2W”)
Figure 37: Start Network Share Enum Job
Figure 38: Continue Enum Job
Figure 39: Network Share Connection Attempt
Similar to the previous process, files on the network share(s) are then discovered and iterated through (“FindFirstFileW” and “FindNextFileW”), to be stored and used by the network share file encrypt job.
Figure 40: Network Share File Iteration
With the network share files discovered and stored, the encryption job (“encryptJobNS”) for them is started.
Figure 41: Encrypt Network Share Files
Lastly, to cleanup, the application, system, and security event logs are erased (“OpenEventLogA” and “ClearEventLogA”), and a command which pings the localhost address, before deleting the dropped “1.bat” file, and performing a hard restart on the device, is invoked with “WinExec”, before exiting.
Figure 42: Clear Event Logs
Figure 43: Cleanup Commands
Figure 44: Execute Cleanup Commands
Additional data extracted during runtime, and similar LockBit/Darkrace files for comparison.
User or threat actor executes DoNex ransomware binary
Binary starts and hides attached console window
Performs a mutex check to ensure only one instance of the binary is running
Obtains the access token from the current thread, or process
Queries user account info associated with the token
Checks if user account belongs to local administrators group
Disables WOW file system redirection if running under 32-bit Windows, or WOW64 on 64-bit Windows
Drops an icon file in "ProgramData"
Sets dropped icon as default file icon for encrypted files
Wipes recycle bins on all drives
Drops "1.bat" batch file to "ProgramData" and executes it
Enumerates connected drives
Identifies root path on each drive
Iterates through files on drives
Checks files against blacklist
Checks if target files are locked and if true, kill locking process(es)
Encrypts files on disk
Drops ransom note "ReadMe.txt"
Enumerates accessible network shares
Attempts to connect to any open shares
Iterates through files on shares
Encrypts files on network shares
Clears application, security, and system event logs
Deletes "1.bat" file
Forces a hard restart on the device
Takeaway
Unsurprisingly, the threat actors behind the DoNex group are far from innovators in the ransomware landscape, with nothing new brought to the table, outside of renaming some strings within the LockBit builder. DoNex, and the Darkrace ransomware gang are merely trying to shortcut their way to successful compromises, using the scraps left behind by LockBit and the leaked builder. The appearance of these smaller and newer groups will only become more common, as the skill ceiling for successful compromise is pushed down lower, partially due to the affiliate programs larger ransomware families have in place, and the beginner friendly builders, that are directly provided, or in the case of LockBit, leaked.
This week, the SSH protocol made the news due to the now infamous xz-utils backdoor. One of my favorite detection techniques is network traffic analysis. Protocols like SSH make this, first of all, more difficult. However, as I did show in the discussion of SSH identification strings earlier this year, some information is still to be gained from SSH traffic [1].
Let's look at the SSH handshake of a normal SSH client and a normal SSH server in a bit more detail to learn what is normal when it comes to SSH.
1 – Client Identification
The first payload packet sent from the client to the server should only contain the client identification string. Note that the format is standardized. The important part is in the beginning:
SSH-2.0-OpenSSH_9.6
This means we are going to use SSH-2.0.
2 – Server Identification
In reply, the server will send its identification string. As for the client, the beginning of the string identifies the SSH version.
SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u3
3 – Client Key Exchange Init
This is a bit like the "Client Hello" for TLS. It lists all the ciphers the client supports.
4 – Server Key Exchange Init
In the case of TLS, the server would pick the cipher. But for SSH, the server responds with its list of supported ciphers
5 – The client now responds with the selected cipher and its public key
6 – The server now responds to complete the key exchange.
7 – In the end, the client acknowledges the complete exchange with a "New Keys" message.
Everything beyond this point will be encrypted.
For the xz-utils backdoor, Step 5, where the client sends its public key, is the interesting spot. This is where the attacker would send the exploit. However, the key is derived for specific connections and implementations, so I doubt this will be useful for detection.
The zeek documentation dedicates a chapter to understanding SSH and suggests several ways to leverage the zeek ssh.log. The log does not log public keys.
To experiment, we luckily have Anthony Weems' implementation of the backdoor [2]. I ran his "xzbot", and got the following lines in my syslog for a regular, non-backdoored (I hope) Ubuntu 22.04 system:
Connection closed by 10.128.0.11 port 38682 [preauth]
User root from 10.128.0.11 not allowed because none of user's groups are listed in AllowGroups error: userauth_pubkey: parse key: error in libcrypto [preauth]
Connection closed by invalid user root 10.128.0.11 port 38780 [preauth]
I highlighted the third line. It is unique in that I have not seen it before. This could indicate someone is attempting a technique like the one implemented in the backdoor to execute code. Or is it just me using the xzbot wrong? I used the default ed448 seed of 0.
The packet capture appears to be similar.
Please let me know if you have other ideas to detect this backdoor or similar backdoors (better!) via network traffic.
Errata: It turns out I have missed two advisories when going through the CSIRT sites the first time – I have amended the text and table to reflect this.
Unless you took the whole weekend off, you must have seen by now that Andres Freund published an amazing discovery on Friday on the Openwall mailing list (https://www.openwall.com/lists/oss-security/2024/03/29/4).
(c) SANS Internet Storm Center. https://isc.sans.edu Creative Commons Attribution-Noncommercial 3.0 United States License.
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