Linux Base64 Encoded Pipe to Shell

A Sigma rule for process creation on Linux, by pH-T (Nextron Systems).

medium 1 ATT&CK technique

What it looks for

its detection, as SigmaHQ writes it

detection:
  selection_base64:
    CommandLine|contains: 'base64 '
  selection_exec:
    - CommandLine|contains:
        - '| bash '
        - '| sh '
        - '|bash '
        - '|sh '
    - CommandLine|endswith:
        - ' |sh'
        - '| bash'
        - '| sh'
        - '|bash'
  condition: all of selection_*

The rule’s detection, its selections and fields in order of name. The whole rule, with its references and false positives, is on SigmaHQ, by pH-T (Nextron Systems), under the Detection Rule License 1.1. CmdID evaluates it on a command line alone: a test on what a command line cannot show, such as the parent process or the user, is not met.

None of the everyday examples and documented commands on CmdID’s program pages trips it. To see whether a command line does, paste it into CmdID.

ATT&CK

the techniques it is tagged with

T1140Deobfuscate/Decode Files or Information

Linux Base64 Encoded Pipe to Shell

What it looks for

ATT&CK

Other rules for T1140 Deobfuscate/Decode Files or Information