LoFP / directories /dev/shm and /run/shm are temporary file storage directories in linux. they are intended to appear as a mounted file system, but uses virtual memory instead of a persistent storage device and thus are used for mounting file systems in legitimate purposes.

Techniques

• T1059

Sample rules

Binary Executed from Shared Memory Directory

• source: elastic
• technicques:
  • T1059

Description

Identifies the execution of a binary by root in Linux shared memory directories: (/dev/shm/, /run/shm/, /var/run/, /var/lock/). This activity is to be considered highly abnormal and should be investigated. Threat actors have placed executables used for persistence on high-uptime servers in these directories as system backdoors.

Detection logic

process where host.os.type == "linux" and event.type == "start" and event.action in ("exec", "exec_event") and
user.id == "0" and process.executable : ("/dev/shm/*", "/run/shm/*", "/var/run/*", "/var/lock/*") and
not process.executable : ("/var/run/docker/*", "/var/run/utsns/*", "/var/run/s6/*", "/var/run/cloudera-scm-agent/*", 
"/var/run/argo/argoexec") and not process.parent.command_line : "/usr/bin/runc init"