MemProcFS Usage for Memory Dump Mounting and Credential Access

MemProcFS is a memory forensics tool that allows users to mount physical memory as a virtual file system. While legitimate uses exist for forensic analysis, adversaries are abusing it to gain unauthorized access to sensitive information. Observed tactics involve mounting memory dumps of compromised systems and extracting credentials, LSA secrets, SAM data, and cached domain credentials. This activity is particularly concerning as it allows threat actors to bypass traditional security measures and directly access sensitive data within the memory space of targeted processes. Unapproved usage of MemProcFS should be considered suspicious and investigated immediately to prevent credential theft and lateral movement.

Attack Chain

1. The attacker gains initial access to a system through unspecified means (e.g., exploiting a vulnerability or using stolen credentials).
2. The attacker obtains a memory dump of the compromised system, which may contain sensitive information.
3. The attacker executes MemProcFS.exe with the -device parameter to mount the memory dump as a virtual file system.
4. MemProcFS creates a virtual file system representation of the memory dump, allowing the attacker to browse the memory space as files and directories.
5. The attacker accesses the memory of the LSASS process (lsass.exe) through the mounted file system.
6. The attacker extracts credentials, such as usernames and passwords, from the LSASS process memory.
7. The attacker may also access registry hives through the mounted file system to obtain LSA secrets, SAM data, and cached domain credentials.
8. The attacker uses the stolen credentials for lateral movement, privilege escalation, or data exfiltration.

Impact

Successful exploitation allows threat actors to steal sensitive information, including credentials, LSA secrets, SAM data, and cached domain credentials. Compromised credentials can be used for lateral movement within the network, privilege escalation, and further data breaches. The number of potential victims is unknown, but the severity of the impact is high due to the potential for widespread compromise. Sectors at risk include any organization that stores sensitive data on Windows systems.

Recommendation

• Deploy the Sigma rule “Detect MemProcFS Execution with Device Parameter” to your SIEM to identify suspicious use of MemProcFS based on process creation events.
• Enable Sysmon process creation logging to provide the necessary data for the Sigma rules above.
• Monitor for unusual file system access patterns that may indicate a memory dump being mounted as a virtual file system.