Sigma rule: Syslog Clearing or Removal Via System Utilities

Rule

Title

Syslog Clearing or Removal Via System Utilities

Status

test

Level

high

Author

Max Altgelt (Nextron Systems), Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research), MSTIC

Date

2021-10-15

Modified

2025-10-15

File

rules/linux/process_creation/proc_creation_lnx_clear_syslog.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects specific commands commonly used to remove or empty the syslog. Which is a technique often used by attacker as a method to hide their tracks

Log source

product

linux

category

process_creation

Detection

selection_file:
    CommandLine|contains: '/var/log/syslog'
selection_command_rm:
    # Examples:
    #   rm -f /var/log/syslog
    Image|endswith: '/rm'
    CommandLine|contains:
        - ' -r '
        - ' -f '
        - ' -rf '
        - '/var/log/syslog' # We use this to avoid re-writing a separate selection
selection_command_unlink:
    # Examples:
    #   unlink /var/log/syslog
    Image|endswith: '/unlink'
selection_command_mv:
    # Examples:
    #   mv /var/log/syslog
    Image|endswith: '/mv'
selection_command_truncate:
    # Examples:
    #   truncate --size 0 /var/log/syslog
    Image|endswith: '/truncate'
    CommandLine|contains|all:
        - '0 '
        - '/var/log/syslog' # We use this to avoid re-writing a separate selection
    CommandLine|contains:
        - '-s '
        - '-c '
        - '--size'
selection_command_ln:
    # Examples:
    #   ln -sfn /dev/null /var/log/syslog
    Image|endswith: '/ln'
    CommandLine|contains|all:
        - '/dev/null '
        - '/var/log/syslog' # We use this to avoid re-writing a separate selection
    CommandLine|contains:
        - '-sf '
        - '-sfn '
        - '-sfT '
selection_command_cp:
    # Examples:
    #   cp /dev/null /var/log/syslog
    Image|endswith: '/cp'
    CommandLine|contains: '/dev/null'
selection_command_shred:
    # Examples:
    #   shred -u /var/log/syslog
    Image|endswith: '/shred'
    CommandLine|contains: '-u '
selection_unique_other:
    CommandLine|contains:
        - ' > /var/log/syslog'
        - ' >/var/log/syslog'
        - ' >| /var/log/syslog'  # redirection empties w spacing, noclobber
        - ': > /var/log/syslog'
        - ':> /var/log/syslog'
        - ':>/var/log/syslog'
        - '>|/var/log/syslog'
selection_unique_journalctl:
    CommandLine|contains:
        - 'journalctl --vacuum'
        - 'journalctl --rotate' # archives current journal files and creates new empty ones
condition: (selection_file and 1 of selection_command_*) or 1 of selection_unique_*

False positives (as the rule lists them)

• Log rotation.
• Maintenance.

Tags

• attack.defense-impairment
• attack.t1685.006

MITRE ATT&CK ids this rule names

• T1685.006

References

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1070.002/T1070.002.md
• https://www.virustotal.com/gui/file/54d60fd58d7fa3475fa123985bfc1594df26da25c1f5fbc7dfdba15876dd8ac5/behavior

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/linux/process_creation/proc_creation_lnx_clear_syslog.yml