Detectionhightest

Binary Padding - MacOS

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.

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Igor Fits, Mikhail Larin, oscd.communityCreated Mon Oct 19Updated Fri Feb 1795361ce5-c891-4b0a-87ca-e24607884a96macos

Log Source

macOSProcess Creation

ProductmacOS← raw: macos

CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic

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_*