Potential Mpclient.DLL Sideloading Via Defender Binaries

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Bhabesh Raj
Source: github.com/SigmaHQ/sigma

Detects potential sideloading of "mpclient.dll" by Windows Defender processes ("MpCmdRun" and "NisSrv") from their non-default directory.

Known false positives

Unlikely

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1574.001` Hijack Execution Flow: DLL
Stealth	`T1574.001` Hijack Execution Flow: DLL

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Potential Mpclient.DLL Sideloading Via Defender Binaries
id: 7002aa10-b8d4-47ae-b5ba-51ab07e228b9
related:
    - id: 418dc89a-9808-4b87-b1d7-e5ae0cb6effc
      type: similar
status: test
description: Detects potential sideloading of "mpclient.dll" by Windows Defender processes ("MpCmdRun" and "NisSrv") from their non-default directory.
references:
    - https://www.sentinelone.com/blog/living-off-windows-defender-lockbit-ransomware-sideloads-cobalt-strike-through-microsoft-security-tool
author: Bhabesh Raj
date: 2022-08-01
modified: 2023-08-04
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.execution
    - attack.stealth
    - attack.t1574.001
logsource:
    product: windows
    category: process_creation
detection:
    selection:
        Image|endswith:
            - '\MpCmdRun.exe'
            - '\NisSrv.exe'
    filter_main_known_locations:
        Image|startswith:
            - 'C:\Program Files (x86)\Windows Defender\'
            - 'C:\Program Files\Microsoft Security Client\'
            - 'C:\Program Files\Windows Defender\'
            - 'C:\ProgramData\Microsoft\Windows Defender\Platform\'
            - 'C:\Windows\WinSxS\'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    Image|endswith:
        - '\MpCmdRun.exe'
        - '\NisSrv.exe'

Stage 2: `not filter_main_known_locations`

filter_main_known_locations:
    Image|startswith:
        - 'C:\Program Files (x86)\Windows Defender\'
        - 'C:\Program Files\Microsoft Security Client\'
        - 'C:\Program Files\Windows Defender\'
        - 'C:\ProgramData\Microsoft\Windows Defender\Platform\'
        - 'C:\Windows\WinSxS\'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	starts_with	`C:\Program Files (x86)\Windows Defender\`	`excludes:Image` `field:"Image" value:"C:\Program Files (x86)\Windows Defender\"`
`Image`	starts_with	`C:\Program Files\Microsoft Security Client\`	`excludes:Image` `field:"Image" value:"C:\Program Files\Microsoft Security Client\"`
`Image`	starts_with	`C:\Program Files\Windows Defender\`	`excludes:Image` `field:"Image" value:"C:\Program Files\Windows Defender\"`
`Image`	starts_with	`C:\ProgramData\Microsoft\Windows Defender\Platform\`	`excludes:Image` `field:"Image" value:"C:\ProgramData\Microsoft\Windows Defender\Platform\"`
`Image`	starts_with	`C:\Windows\WinSxS\`	`excludes:Image` `field:"Image" value:"C:\Windows\WinSxS\"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\MpCmdRun.exe` corpus 4 (sigma 4) `\NisSrv.exe` corpus 2 (sigma 2)	`field:"Image" kind:ends_with`