Potential Netcat Reverse Shell Execution

A Sigma rule for process creation on Linux, by @d4ns4n_, Nasreddine Bencherchali (Nextron Systems).

high 1 ATT&CK technique 3 programs it names

What it looks for

its detection, as SigmaHQ writes it

detection:
  selection_flags:
    CommandLine|contains:
      - ' -c '
      - ' -e '
  selection_nc:
    Image|endswith:
      - '/nc.openbsd'
      - '/nc.traditional'
      - '/nc'
      - '/ncat'
      - '/netcat.openbsd'
      - '/netcat.traditional'
      - '/netcat'
  selection_shell:
    CommandLine|contains:
      - ' ash'
      - ' bash'
      - ' bsh'
      - ' csh'
      - ' ksh'
      - ' pdksh'
      - ' sh'
      - ' tcsh'
      - '/bin/ash'
      - '/bin/bash'
      - '/bin/bsh'
      - '/bin/csh'
      - '/bin/ksh'
      - '/bin/pdksh'
      - '/bin/sh'
      - '/bin/tcsh'
      - '/bin/zsh'
      - '$IFSash'
      - '$IFSbash'
      - '$IFSbsh'
      - '$IFScsh'
      - '$IFSksh'
      - '$IFSpdksh'
      - '$IFSsh'
      - '$IFStcsh'
      - '$IFSzsh'
  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 @d4ns4n_, Nasreddine Bencherchali (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.

Command lines that trip it

documented abuse, read by CmdID

The commands documented for busybox, nc trip it: each is on its program’s page, read by CmdID.

Programs and files it names

their pages here

ncncatnetcat

ATT&CK

the techniques it is tagged with

T1059Command and Scripting Interpreter

Potential Netcat Reverse Shell Execution

What it looks for

Command lines that trip it

Programs and files it names

ATT&CK

Other rules for T1059 Command and Scripting Interpreter