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Detection rules › Sigma

Potential Persistence Via Excel Add-in - Registry

Status
test
Severity
high
Log source
category registry_set, product windows
Author
frack113
Source
github.com/SigmaHQ/sigma

Detect potential persistence via the creation of an excel add-in (XLL) file to make it run automatically when Excel is started.

MITRE ATT&CK coverage

TacticTechniques
Persistence

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 13: RegistryEvent (Value Set)

Rule body

title: Potential Persistence Via Excel Add-in - Registry
id: 961e33d1-4f86-4fcf-80ab-930a708b2f82
status: test
description: Detect potential persistence via the creation of an excel add-in (XLL) file to make it run automatically when Excel is started.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/4ae9580a1a8772db87a1b6cdb0d03e5af231e966/atomics/T1137.006/T1137.006.md
    - https://labs.withsecure.com/publications/add-in-opportunities-for-office-persistence
author: frack113
date: 2023-01-15
modified: 2023-08-17
tags:
    - attack.persistence
    - attack.t1137.006
logsource:
    product: windows
    category: registry_set
detection:
    selection:
        TargetObject|contains: 'Software\Microsoft\Office\'
        TargetObject|endswith: '\Excel\Options'
        Details|startswith: '/R '
        Details|endswith: '.xll'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    TargetObject|contains: 'Software\Microsoft\Office\'
    TargetObject|endswith: '\Excel\Options'
    Details|startswith: '/R '
    Details|endswith: '.xll'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
Detailsends_with
  • .xll
field:"Details" kind:ends_with value:".xll"
Detailsstarts_with
  • /R
field:"Details" kind:starts_with value:"/R "
TargetObjectends_with
  • \Excel\Options
field:"TargetObject" kind:ends_with value:"\Excel\Options"
TargetObjectmatch
  • Software\Microsoft\Office\ corpus 2 (sigma 2)
field:"TargetObject" kind:match value:"Software\Microsoft\Office\"