detection.wiki

Detection rules › Sigma

AgentExecutor PowerShell Execution

Status
test
Severity
medium
Log source
product windows, category process_creation
Author
Nasreddine Bencherchali (Nextron Systems), memory-shards
Source
github.com/SigmaHQ/sigma

Detects execution of the AgentExecutor.exe binary. Which can be abused as a LOLBIN to execute powershell scripts with the ExecutionPolicy "Bypass" or any binary named "powershell.exe" located in the path provided by 6th positional argument

MITRE ATT&CK coverage

TacticTechniques
StealthT1218 System Binary Proxy Execution

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: AgentExecutor PowerShell Execution
id: 7efd2c8d-8b18-45b7-947d-adfe9ed04f61
related:
    - id: c0b40568-b1e9-4b03-8d6c-b096da6da9ab
      type: similar
status: test
description: Detects execution of the AgentExecutor.exe binary. Which can be abused as a LOLBIN to execute powershell scripts with the ExecutionPolicy "Bypass" or any binary named "powershell.exe" located in the path provided by 6th positional argument
author: Nasreddine Bencherchali (Nextron Systems), memory-shards
references:
    - https://twitter.com/lefterispan/status/1286259016436514816
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Agentexecutor/
    - https://learn.microsoft.com/en-us/mem/intune/apps/intune-management-extension
    - https://twitter.com/jseerden/status/1247985304667066373/photo/1
date: 2022-12-24
modified: 2024-08-07
tags:
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image: '\AgentExecutor.exe'
        - OriginalFileName: 'AgentExecutor.exe'
    selection_cli:
        # Example:
        #   AgentExecutor.exe -powershell [scriptPath] [outputFilePath] [errorFilePath] [timeoutFilePath] [timeoutSeconds] [powershellPath] [enforceSignatureCheck] [runAs32BitOn64]
        # Note:
        #   - If [timeoutSeconds] is NULL then it defaults to 60000
        #   - If [enforceSignatureCheck] is:
        #       - "NULL" or "1" then a PowerShell instance is spawned with the args: "-NoProfile -executionPolicy allsigned -file "
        #       - Else a PowerShell instance is spawned with the args: "-NoProfile -executionPolicy bypass -file "
        #   - [powershellPath] is always concatendated to "powershell.exe"
        CommandLine|contains:
            - ' -powershell' # Also covers the "-powershellDetection" flag
            - ' -remediationScript'
    filter_main_intune:
        ParentImage|endswith: '\Microsoft.Management.Services.IntuneWindowsAgent.exe'
    condition: all of selection_* and not 1 of filter_main_*
falsepositives:
    - Legitimate use via Intune management. You exclude script paths and names to reduce FP rate
level: medium

Stages and Predicates

Stage 0: condition

all of selection_* and not 1 of filter_main_*

Stage 1: selection_img

selection_img:
    - Image: '\AgentExecutor.exe'
    - OriginalFileName: 'AgentExecutor.exe'

Stage 2: selection_cli

selection_cli:
    CommandLine|contains:
        - ' -powershell'
        - ' -remediationScript'

Stage 3: not filter_main_intune

filter_main_intune:
    ParentImage|endswith: '\Microsoft.Management.Services.IntuneWindowsAgent.exe'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
ParentImageends_with\Microsoft.Management.Services.IntuneWindowsAgent.exe

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLinematch
  • -powershell corpus 2 (sigma 2)
  • -remediationScript corpus 2 (sigma 2)
Imageeq
  • \AgentExecutor.exe
OriginalFileNameeq
  • AgentExecutor.exe corpus 2 (sigma 2)