Sysmon Configuration Update

Hunt Hypothesis

Detects updates to Sysmon’s configuration. Attackers might update or replace the Sysmon configuration with a bare bone one to avoid monitoring without shutting down the service completely

Detection Rule

Sigma (Original)

title: Sysmon Configuration Update
id: 87911521-7098-470b-a459-9a57fc80bdfd
status: test
description: Detects updates to Sysmon's configuration. Attackers might update or replace the Sysmon configuration with a bare bone one to avoid monitoring without shutting down the service completely
references:
    - https://learn.microsoft.com/en-us/sysinternals/downloads/sysmon
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-03-09
modified: 2024-03-13
tags:
    - attack.defense-impairment
    - attack.t1685
logsource:
    category: process_creation
    product: windows
detection:
    selection_pe:
        - Image|endswith:
              - \Sysmon64.exe
              - \Sysmon.exe
        - Description: 'System activity monitor'
    selection_cli:
        CommandLine|contains|windash: '-c'
    condition: all of selection_*
falsepositives:
    - Legitimate administrators might use this command to update Sysmon configuration.
level: medium

KQL (Azure Sentinel)

imProcessCreate
| where ((TargetProcessName endswith "\\Sysmon64.exe" or TargetProcessName endswith "\\Sysmon.exe") or TargetProcessFileDescription =~ "System activity monitor") and (TargetProcessCommandLine contains "-c" or TargetProcessCommandLine contains "/c" or TargetProcessCommandLine contains "–c" or TargetProcessCommandLine contains "—c" or TargetProcessCommandLine contains "―c")

Required Data Sources

False Positive Guidance

• Legitimate administrators might use this command to update Sysmon configuration.

MITRE ATT&CK Context

• Technique: T1685 — T1685

References

• https://learn.microsoft.com/en-us/sysinternals/downloads/sysmon
• SigmaHQ Rule