PUA - DefenderCheck Execution

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Florian Roth (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the use of DefenderCheck, a tool to evaluate the signatures used in Microsoft Defender. It can be used to figure out the strings / byte chains used in Microsoft Defender to detect a tool and thus used for AV evasion.

Known false positives

Unlikely

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1027.005` Obfuscated Files or Information: Indicator Removal from Tools

Telemetry coverage

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

Rule body

title: PUA - DefenderCheck Execution
id: f0ca6c24-3225-47d5-b1f5-352bf07ecfa7
status: test
description: Detects the use of DefenderCheck, a tool to evaluate the signatures used in Microsoft Defender. It can be used to figure out the strings / byte chains used in Microsoft Defender to detect a tool and thus used for AV evasion.
references:
    - https://github.com/matterpreter/DefenderCheck
author: Florian Roth (Nextron Systems)
date: 2022-08-30
modified: 2023-02-04
tags:
    - attack.stealth
    - attack.t1027.005
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith: '\DefenderCheck.exe'
        - Description: 'DefenderCheck'
    condition: selection
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    - Image|endswith: '\DefenderCheck.exe'
    - Description: 'DefenderCheck'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Description`	eq	`DefenderCheck`	`field:"Description" kind:eq value:"DefenderCheck"`
`Image`	ends_with	`\DefenderCheck.exe`	`field:"Image" kind:ends_with value:"\DefenderCheck.exe"`