Proc Filesystem

What the technique is

Adversaries may gather credentials from the proc filesystem or /proc. The proc filesystem is a pseudo-filesystem used as an interface to kernel data structures for Linux based systems managing virtual memory. For each process, the /proc//maps file shows how memory is mapped within the process’s virtual address space. And /proc//mem, exposed for debugging purposes, provides access to the process’s virtual address space. When executing with root privileges, adversaries can search these memory locations for all processes on a system that contain patterns indicative of credentials. Adversaries may use regex patterns, such as grep -E "^[0-9a-f-]* r" /proc/"$pid"/maps | cut -d' ' -f 1, to look for fixed strings in memory structures or cached hashes. When running without privileged access, processes can still view their own virtual memory locations. Some services or programs may save credentials in clear text inside the process’s memory. If running as or with the permissions of a web browser, a process can search the /maps & /mem locations for common website credential patterns (that can also be used to find adjacent memory within the same structure) in which hashes or cleartext credentials may be located.

What MITRE says you would watch

• AN1631

  Monitoring adversary access to sensitive process memory via the /proc filesystem to extract credential material, often involving multi-step access to /proc/[pid]/mem or /proc/[pid]/maps combined with privilege escalation or credential scraping binaries.