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Detection rules › Sigma

Change the Fax Dll

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

Detect possible persistence using Fax DLL load when service restart

MITRE ATT&CK coverage

TacticTechniques
Persistence
Defense Impairment

Telemetry coverage

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

Rule body

title: Change the Fax Dll
id: 9e3357ba-09d4-4fbd-a7c5-ad6386314513
status: test
description: Detect possible persistence using Fax DLL load when service restart
references:
    - https://twitter.com/dottor_morte/status/1544652325570191361
    - https://raw.githubusercontent.com/RiccardoAncarani/talks/master/F-Secure/unorthodox-lateral-movement.pdf
author: frack113
date: 2022-07-17
modified: 2022-12-30
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    product: windows
    category: registry_set
detection:
    selection:
        TargetObject|contains|all:
            - '\Software\Microsoft\Fax\Device Providers\'
            - '\ImageName'
    filter:
        Details: '%systemroot%\system32\fxst30.dll' # Windows 10
    condition: selection and not filter
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection and not filter

Stage 1: selection

selection:
    TargetObject|contains|all:
        - '\Software\Microsoft\Fax\Device Providers\'
        - '\ImageName'

Stage 2: not filter

filter:
    Details: '%systemroot%\system32\fxst30.dll'

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
Detailseq%systemroot%\system32\fxst30.dllexcludes:Details field:"Details" value:"%systemroot%\system32\fxst30.dll"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
TargetObjectmatch
  • \ImageName
  • \Software\Microsoft\Fax\Device Providers\
field:"TargetObject" kind:match