RunMRU Registry Key Deletion

Status: experimental
Severity: high
Log source: category process_creation, product windows
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects deletion of the RunMRU registry key, which stores the history of commands executed via the Run dialog. In the clickfix techniques, the phishing lures instruct users to open a run dialog through (Win + R) and execute malicious commands. Adversaries may delete this key to cover their tracks after executing commands.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1070.003` Indicator Removal: Clear Command History

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: RunMRU Registry Key Deletion
id: c11aecef-9c37-45a6-9c07-bc0782f963fd
related:
    - id: 3a9b8c1e-5b2e-4f7a-9d1c-2a7f3b6e1c55
      type: similar
status: experimental
description: |
    Detects deletion of the RunMRU registry key, which stores the history of commands executed via the Run dialog.
    In the clickfix techniques, the phishing lures instruct users to open a run dialog through (Win + R) and execute malicious commands.
    Adversaries may delete this key to cover their tracks after executing commands.
references:
    - https://www.zscaler.com/blogs/security-research/coldriver-updates-arsenal-baitswitch-and-simplefix
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-09-25
tags:
    - attack.stealth
    - attack.t1070.003
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\reg.exe'
        - OriginalFileName: 'reg.exe'
    selection_cli:
        CommandLine|contains|all:
            - ' del'
            - '\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\reg.exe'
    - OriginalFileName: 'reg.exe'

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains|all:
        - ' del'
        - '\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`del` corpus 3 (splunk 2, sigma 1) `\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU`	`field:"CommandLine" kind:match`
`Image`	ends_with	`\reg.exe` corpus 58 (sigma 58)	`field:"Image" kind:ends_with value:"\reg.exe"`
`OriginalFileName`	eq	`reg.exe` corpus 43 (sigma 32, splunk 8, elastic 3)	`field:"OriginalFileName" kind:eq value:"reg.exe"`