Binary Padding - MacOS

A Sigma rule for process creation on macOS, by Igor Fits, Mikhail Larin, oscd.community.

high 1 ATT&CK technique 2 programs it names 1 everyday example trips it

What it looks for

its detection, as SigmaHQ writes it

detection:
  selection_dd:
    CommandLine|contains:
      - 'if=/dev/zero'
      - 'if=/dev/random'
      - 'if=/dev/urandom'
    Image|endswith: '/dd'
  selection_truncate:
    CommandLine|contains: '-s +'
    Image|endswith: '/truncate'
  condition: 1 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 Igor Fits, Mikhail Larin, oscd.community, 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

everyday examples from tldr-pages, CC BY 4.0, each read by CmdID

Generate a file with a specific number of random bytes by using kernel random driver on the page for dd

dd bs=100 count=1 if=/dev/urandom of=path/to/random_fileIdentify

Programs and files it names

their pages here

ddtruncate

ATT&CK

the techniques it is tagged with

T1027.001Obfuscated Files or Information: Binary Padding