PUA - DefenderCheck Execution

Hunt Hypothesis

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 t

Detection Rule

Sigma (Original)

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

KQL (Azure Sentinel)

imProcessCreate
| where TargetProcessName endswith "\\DefenderCheck.exe" or TargetProcessFileDescription =~ "DefenderCheck"

Required Data Sources

False Positive Guidance

• Unlikely

MITRE ATT&CK Context

• Technique: T1027.005 — T1027.005

References

• https://github.com/matterpreter/DefenderCheck
• SigmaHQ Rule