Detection rules › Sigma
Clear or Disable Kernel Ring Buffer Logs via Syslog Syscall
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 attackers to hide traces after exploitation or privilege escalation. A common technique is running dmesg -c, which triggers this syscall internally.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Defense Impairment | T1685.006 Disable or Modify Tools: Clear Linux or Mac System Logs |
Event coverage
| Provider | Event |
|---|---|
| Linux-Auditd | Event ID 1300 |
Rule body yaml
title: Clear or Disable Kernel Ring Buffer Logs via Syslog Syscall
id: eca5e022-d368-4043-98e5-9736fb01f72f
status: experimental
description: |
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 attackers to hide traces after exploitation
or privilege escalation. A common technique is running `dmesg -c`, which triggers this syscall internally.
references:
- https://man7.org/linux/man-pages/man2/syslog.2.html
- https://man7.org/linux/man-pages/man1/dmesg.1.html
author: Milad Cheraghi
date: 2025-05-27
modified: 2025-12-05
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 # SYSLOG_ACTION_READ_CLEAR : Read and clear log
- 5 # SYSLOG_ACTION_CLEAR: Clear kernel ring buffer (without reading)
- 6 # SYSLOG_ACTION_CONSOLE_OFF: Disable logging to console
condition: selection
falsepositives:
- System administrators or scripts that intentionally clear logs
- Debugging scripts
level: medium
Stages and Predicates
Stage 0: condition
selectionStage 1: selection
selection:
type: 'SYSCALL'
SYSCALL: 'syslog'
a0:
- 4
- 5
- 6
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.