Windows Recovery Environment Disabled Via Reagentc

Status: experimental
Severity: medium
Log source: category process_creation, product windows
Author: Daniel Koifman (KoifSec), Michael Vilshin
Source: github.com/SigmaHQ/sigma

Detects attempts to disable windows recovery environment using Reagentc. ReAgentc.exe is a command-line tool in Windows used to manage the Windows Recovery Environment (WinRE). It allows users to enable, disable, and configure WinRE, which is used for troubleshooting and repairing common boot issues.

Known false positives

Legitimate administrative activity

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1490` Inhibit System Recovery

Telemetry coverage

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

Rule body

title: Windows Recovery Environment Disabled Via Reagentc
id: db1c21e4-cd66-4b4e-85ca-590f0780529c
status: experimental
description: |
    Detects attempts to disable windows recovery environment using Reagentc.
    ReAgentc.exe is a command-line tool in Windows used to manage the Windows Recovery Environment (WinRE).
    It allows users to enable, disable, and configure WinRE, which is used for troubleshooting and repairing common boot issues.
references:
    - https://www.elastic.co/security-labs/maas-appeal-an-infostealer-rises-from-the-ashes
    - https://learn.microsoft.com/en-us/windows-hardware/manufacture/desktop/reagentc-command-line-options?view=windows-11
author: Daniel Koifman (KoifSec), Michael Vilshin
date: 2025-07-31
tags:
    - attack.impact
    - attack.t1490
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:   # Example command simulated:  reagentc /disable
        - Image|endswith: '\reagentc.exe'
        - OriginalFileName: 'reagentc.exe'
    selection_cli:
        CommandLine|contains|windash: '/disable'
    condition: all of selection_*
falsepositives:
    - Legitimate administrative activity
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

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

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains|windash: '/disable'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`/disable` transforms: `windash` corpus 3 (sigma 2, splunk 1)	`field:"CommandLine" kind:match value:"/disable"`
`Image`	ends_with	`\reagentc.exe`	`field:"Image" kind:ends_with value:"\reagentc.exe"`
`OriginalFileName`	eq	`reagentc.exe`	`field:"OriginalFileName" kind:eq value:"reagentc.exe"`