AddinUtil.EXE Execution From Uncommon Directory

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Michael McKinley (@McKinleyMike), Tony Latteri (@TheLatteri)
Source: github.com/SigmaHQ/sigma

Detects execution of the Add-In deployment cache updating utility (AddInutil.exe) from a non-standard directory.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1218` System Binary Proxy Execution

Telemetry coverage

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

Rule body

title: AddinUtil.EXE Execution From Uncommon Directory
id: 6120ac2a-a34b-42c0-a9bd-1fb9f459f348
status: test
description: Detects execution of the Add-In deployment cache updating utility (AddInutil.exe) from a non-standard directory.
references:
    - https://www.blue-prints.blog/content/blog/posts/lolbin/addinutil-lolbas.html
author: Michael McKinley (@McKinleyMike), Tony Latteri (@TheLatteri)
date: 2023-09-18
modified: 2025-02-24
tags:
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith: '\addinutil.exe'
        - OriginalFileName: 'AddInUtil.exe'
    filter_main_legit_location:
        Image|contains:
            - ':\Windows\Microsoft.NET\Framework\'
            - ':\Windows\Microsoft.NET\Framework64\'
            - ':\Windows\Microsoft.NET\FrameworkArm\'
            - ':\Windows\Microsoft.NET\FrameworkArm64\'
            - ':\Windows\WinSxS\'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    - Image|endswith: '\addinutil.exe'
    - OriginalFileName: 'AddInUtil.exe'

Stage 2: `not filter_main_legit_location`

filter_main_legit_location:
    Image|contains:
        - ':\Windows\Microsoft.NET\Framework\'
        - ':\Windows\Microsoft.NET\Framework64\'
        - ':\Windows\Microsoft.NET\FrameworkArm\'
        - ':\Windows\Microsoft.NET\FrameworkArm64\'
        - ':\Windows\WinSxS\'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	match	`:\Windows\Microsoft.NET\Framework64\`	`excludes:Image` `field:"Image" value:":\Windows\Microsoft.NET\Framework64\"`
`Image`	match	`:\Windows\Microsoft.NET\FrameworkArm64\`	`excludes:Image` `field:"Image" value:":\Windows\Microsoft.NET\FrameworkArm64\"`
`Image`	match	`:\Windows\Microsoft.NET\FrameworkArm\`	`excludes:Image` `field:"Image" value:":\Windows\Microsoft.NET\FrameworkArm\"`
`Image`	match	`:\Windows\Microsoft.NET\Framework\`	`excludes:Image` `field:"Image" value:":\Windows\Microsoft.NET\Framework\"`
`Image`	match	`:\Windows\WinSxS\`	`excludes:Image` `field:"Image" value:":\Windows\WinSxS\"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\addinutil.exe` corpus 4 (sigma 4)	`field:"Image" kind:ends_with value:"\addinutil.exe"`
`OriginalFileName`	eq	`AddInUtil.exe` corpus 4 (sigma 3, elastic 1)	`field:"OriginalFileName" kind:eq value:"AddInUtil.exe"`