ShimCache Flush — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: stable; severity: high. Source dates: 2021-02-01 / not supplied.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 2248b4d2397f49e2efce6167be23761b218370db7755f1b4919cae30328d29e9

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: ShimCache Flush
id: b0524451-19af-4efa-a46f-562a977f792e
status: stable
description: Detects actions that clear the local ShimCache and remove forensic evidence
references:
    - https://medium.com/@blueteamops/shimcache-flush-89daff28d15e
author: Florian Roth (Nextron Systems)
date: 2021-02-01
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    category: process_creation
    product: windows
detection:
    selection1a:
        CommandLine|contains|all:
            - 'rundll32'
            - 'apphelp.dll'
    selection1b:
        CommandLine|contains:
            - 'ShimFlushCache'
            - '#250'
    selection2a:
        CommandLine|contains|all:
            - 'rundll32'
            - 'kernel32.dll'
    selection2b:
        CommandLine|contains:
            - 'BaseFlushAppcompatCache'
            - '#46'
    condition: ( selection1a and selection1b ) or ( selection2a and selection2b )
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://medium.com/@blueteamops/shimcache-flush-89daff28d15e