Sigma rule: Potentially Suspicious Wuauclt Network Connection

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-79a98c418d30, updated 2024-03-12T00:00:00.000Z.

Rule

Title: Potentially Suspicious Wuauclt Network Connection
Status: test
Level: medium
Author: Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research)
Date: 2020-10-12
Modified: 2024-03-12
File: rules/windows/network_connection/net_connection_win_wuauclt_network_connection.yml
Commit: ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the use of the Windows Update Client binary (wuauclt.exe) to proxy execute code and making network connections.
One could easily make the DLL spawn a new process and inject to it to proxy the network connection and bypass this rule.

Log source

product: windows
category: network_connection
definition: Requirements: The CommandLine field enrichment is required in order for this rule to be used.

Detection

selection:
    Image|contains: 'wuauclt'
    CommandLine|contains: ' /RunHandlerComServer'
# "C:\WINDOWS\uus\AMD64\wuauclt.exe" /DeploymentHandlerFullPath \\?\C:\Windows\UUS\AMD64\UpdateDeploy.dll /ClassId aaa256e1-5b21-4993-9188-18f07ccb3b98 /RunHandlerComServer
filter_main_ip:
    DestinationIp|cidr: # Ranges excluded based on https://github.com/SigmaHQ/sigma/blob/0f176092326ab9d1e19384d30224e5f29f760d82/rules/windows/network_connection/net_connection_win_dllhost_net_connections.yml
        - '127.0.0.0/8'
        - '10.0.0.0/8'
        - '169.254.0.0/16'  # link-local address
        - '172.16.0.0/12'
        - '192.168.0.0/16'
        - '::1/128'  # IPv6 loopback
        - 'fe80::/10'  # IPv6 link-local addresses
        - 'fc00::/7'  # IPv6 private addresses
filter_main_msrange:  # Sysmon
    DestinationIp|cidr:
        - '20.184.0.0/13' # Microsoft Corporation
        - '20.192.0.0/10' # Microsoft Corporation
        - '23.79.0.0/16' # Microsoft Corporation
        - '51.10.0.0/15'
        - '51.103.0.0/16' # Microsoft Corporation
        - '51.104.0.0/15' # Microsoft Corporation
        - '52.224.0.0/11' # Microsoft Corporation
filter_main_uus:
    CommandLine|contains:
        - ':\Windows\UUS\Packages\Preview\amd64\updatedeploy.dll /ClassId'
        - ':\Windows\UUS\amd64\UpdateDeploy.dll /ClassId'
filter_main_winsxs:
    CommandLine|contains|all:
        - ':\Windows\WinSxS\'
        - '\UpdateDeploy.dll /ClassId '
filter_main_cli_null:
    CommandLine: null
filter_main_cli_empty:
    CommandLine: ''
condition: selection and not 1 of filter_main_*

False positives (as the rule lists them)

Unknown

MITRE ATT&CK ids this rule names

T1218

References

https://dtm.uk/wuauclt/

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/network_connection/net_connection_win_wuauclt_network_connection.yml

Sources and licences

SigmaHQ
"Potentially Suspicious Wuauclt Network Connection" by Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/network_connection/net_connection_win_wuauclt_network_connection.yml.
Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License
Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Potentially Suspicious Wuauclt Network Connection",
entity page, dataset version ref-79a98c418d30, updated 2024-03-12T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/c649a6c7-cd8c-4a78-9c04-000fc76df954 (accessed 2026-11-03).
Underlying source: SigmaHQ rule c649a6c7-cd8c-4a78-9c04-000fc76df954, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.