Suspicious CertReq Command to Download

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

Detects a suspicious CertReq execution downloading a file. This behavior is often used by attackers to download additional payloads or configuration files. Certreq is a built-in Windows utility used to request and retrieve certificates from a certification authority (CA). However, it can be abused by threat actors for malicious purposes.

Known false positives

Unlikely

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1105` Ingress Tool Transfer

Telemetry coverage

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

Rule body

title: Suspicious CertReq Command to Download
id: 4480827a-9799-4232-b2c4-ccc6c4e9e12b
status: experimental
description: |
    Detects a suspicious CertReq execution downloading a file.
    This behavior is often used by attackers to download additional payloads or configuration files.
    Certreq is a built-in Windows utility used to request and retrieve certificates from a certification authority (CA). However, it can be abused by threat actors for malicious purposes.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Certreq/
author: Christian Burkard (Nextron Systems)
date: 2021-11-24
modified: 2025-10-29
tags:
    - attack.command-and-control
    - attack.t1105
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\certreq.exe'
        - OriginalFileName: 'CertReq.exe'
    selection_cli_flag_post:
        CommandLine|contains|windash: '-Post'
    selection_cli_flag_config:
        CommandLine|contains|windash: '-config'
    selection_cli_http:
        CommandLine|contains: 'http'
    condition: all of selection_*
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\certreq.exe'
    - OriginalFileName: 'CertReq.exe'

Stage 2: `selection_cli_flag_post`

selection_cli_flag_post:
    CommandLine|contains|windash: '-Post'

Stage 3: `selection_cli_flag_config`

selection_cli_flag_config:
    CommandLine|contains|windash: '-config'

Stage 4: `selection_cli_http`

selection_cli_http:
    CommandLine|contains: 'http'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-Post` transforms: `windash` `-config` transforms: `windash` `http` corpus 52 (sigma 34, elastic 15, chronicle 2, splunk 1)	`field:"CommandLine" kind:match`
`Image`	ends_with	`\certreq.exe` corpus 7 (sigma 7)	`field:"Image" kind:ends_with value:"\certreq.exe"`
`OriginalFileName`	eq	`CertReq.exe` corpus 5 (elastic 4, sigma 1)	`field:"OriginalFileName" kind:eq value:"CertReq.exe"`