Detection rules › Sigma

Suspicious Windows Update Agent Empty Cmdline

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects suspicious Windows Update Agent activity in which a wuauclt.exe process command line doesn't contain any command line flags

MITRE ATT&CK coverage

TacticTechniques
StealthT1036 Masquerading

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: Suspicious Windows Update Agent Empty Cmdline
id: 52d097e2-063e-4c9c-8fbb-855c8948d135
status: test
description: |
    Detects suspicious Windows Update Agent activity in which a wuauclt.exe process command line doesn't contain any command line flags
references:
    - https://redcanary.com/blog/blackbyte-ransomware/
author: Florian Roth (Nextron Systems)
date: 2022-02-26
modified: 2023-11-11
tags:
    - attack.stealth
    - attack.t1036
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\Wuauclt.exe'
        - OriginalFileName: 'Wuauclt.exe'
    selection_cli:
        CommandLine|endswith:
            - 'Wuauclt'
            - 'Wuauclt.exe'
    condition: all of selection*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

all of selection*

Stage 1: selection_img

selection_img:
    - Image|endswith: '\Wuauclt.exe'
    - OriginalFileName: 'Wuauclt.exe'

Stage 2: selection_cli

selection_cli:
    CommandLine|endswith:
        - 'Wuauclt'
        - 'Wuauclt.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
CommandLineends_with
  • Wuauclt
  • Wuauclt.exe
Imageends_with
  • \Wuauclt.exe corpus 3 (sigma 3)
OriginalFileNameeq
  • Wuauclt.exe corpus 3 (sigma 2, elastic 1)