Suspicious Clear or Disable Kernel Ring Buffer Logs through Syslog Syscall (via auditd)

title: Suspicious Clear or Disable Kernel Ring Buffer Logs through Syslog Syscall (via auditd)
id: b43f0729-d9b9-5a0b-af26-e5ebdaf857ab
status: stable
description: This rule detects the use of the `syslog` syscall with action code 5 (SYSLOG_ACTION_CLEAR), (4 is SYSLOG_ACTION_READ_CLEAR and 6 is SYSLOG_ACTION_CONSOLE_OFF) which clears the kernel ring buffer (dmesg logs). This can be used by adversaries to hide traces after exploitation or privilege escalation. A common method is running `dmesg -c`, which triggers this syscall internally.
references:
    - https://attack.mitre.org/techniques/T1685/006/
    - https://man7.org/linux/man-pages/man2/syslog.2.html
    - https://man7.org/linux/man-pages/man1/dmesg.1.html
author: Huntrule Team
date: 2026-01-20
tags:
    - attack.defense-impairment
    - attack.t1685.006
logsource:
    product: linux
    service: auditd
    definition: |
        Required auditd configuration:
        -a always,exit -F arch=b64 -S syslog -F a0=4 -k clear_dmesg_logs
        -a always,exit -F arch=b64 -S syslog -F a0=5 -k clear_dmesg_logs
        -a always,exit -F arch=b64 -S syslog -F a0=6 -k disable_dmesg_logs
        -a always,exit -F arch=b32 -S syslog -F a0=4 -k clear_dmesg_logs
        -a always,exit -F arch=b32 -S syslog -F a0=5 -k clear_dmesg_logs
        -a always,exit -F arch=b32 -S syslog -F a0=6 -k disable_dmesg_logs
detection:
    selection:
        type: 'SYSCALL'
        SYSCALL: 'syslog'
        a0:
            - 4
            - 5
            - 6
    condition: selection
falsepositives:
    - Unknown
level: medium