Suspicious Vsls-Agent Command With AgentExtensionPath Load

Hunt Hypothesis

Detects Microsoft Visual Studio vsls-agent.exe lolbin execution with a suspicious library load using the —agentExtensionPath parameter

Detection Rule

Sigma (Original)

title: Suspicious Vsls-Agent Command With AgentExtensionPath Load
id: 43103702-5886-11ed-9b6a-0242ac120002
status: test
description: Detects Microsoft Visual Studio vsls-agent.exe lolbin execution with a suspicious library load using the --agentExtensionPath parameter
references:
    - https://twitter.com/bohops/status/1583916360404729857
author: bohops
date: 2022-10-30
tags:
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\vsls-agent.exe'
        CommandLine|contains: '--agentExtensionPath'
    filter:
        CommandLine|contains: 'Microsoft.VisualStudio.LiveShare.Agent.'
    condition: selection and not filter
falsepositives:
    - False positives depend on custom use of vsls-agent.exe
level: medium

KQL (Azure Sentinel)

imProcessCreate
| where (TargetProcessName endswith "\\vsls-agent.exe" and TargetProcessCommandLine contains "--agentExtensionPath") and (not(TargetProcessCommandLine contains "Microsoft.VisualStudio.LiveShare.Agent."))

Required Data Sources

False Positive Guidance

• False positives depend on custom use of vsls-agent.exe

MITRE ATT&CK Context

• Technique: T1218 — T1218

References

• https://twitter.com/bohops/status/1583916360404729857
• SigmaHQ Rule