title: Binary Padding - MacOS
id: 95361ce5-c891-4b0a-87ca-e24607884a96
status: test
description: Adversaries may use binary padding to add junk data and change the on-disk representation of malware. This rule detect using dd and truncate to add a junk data to file.
references:
- https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1027.001/T1027.001.md
- https://linux.die.net/man/1/truncate
- https://linux.die.net/man/1/dd
author: 'Igor Fits, Mikhail Larin, oscd.community'
date: 2020-10-19
modified: 2023-02-17
tags:
- attack.stealth
- attack.t1027.001
logsource:
product: macos
category: process_creation
detection:
selection_truncate:
Image|endswith: '/truncate'
CommandLine|contains: '-s +'
selection_dd:
Image|endswith: '/dd'
CommandLine|contains:
- 'if=/dev/zero' # if input is not /dev/zero, then there is no null padding
- 'if=/dev/random' # high-quality random data
- 'if=/dev/urandom' # low-quality random data
condition: 1 of selection_*
falsepositives:
- Legitimate script work
level: high