Sigma rule: Rundll32 Internet Connection

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-ccaf19063764, updated 2024-03-13T00:00:00.000Z.

Rule

Title
Rundll32 Internet Connection
Status
test
Level
medium
Author
Florian Roth (Nextron Systems)
Date
2017-11-04
Modified
2024-03-13
File
rules/windows/network_connection/net_connection_win_rundll32_net_connections.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects a rundll32 that communicates with public IP addresses

Log source

product
windows
category
network_connection

Detection

selection:
    Image|endswith: '\rundll32.exe'
    Initiated: 'true'
filter_main_local_ranges:
    DestinationIp|cidr:
        - '127.0.0.0/8'
        - '10.0.0.0/8'
        - '172.16.0.0/12'
        - '192.168.0.0/16'
        - '169.254.0.0/16'
        - '::1/128'  # IPv6 loopback
        - 'fe80::/10'  # IPv6 link-local addresses
        - 'fc00::/7'  # IPv6 private addresses
filter_main_ms_ranges:
    DestinationIp|cidr:
        - '20.0.0.0/8' # Microsoft range, caused some FPs
        - '51.103.0.0/16' # Microsoft AS8075 range, caused some FPs
        - '51.104.0.0/16' # Microsoft AS8075 range, caused some FPs
        - '51.105.0.0/16' # Microsoft AS8075 range, caused some FPs
filter_main_app_sdb:
    CommandLine|endswith: '\system32\PcaSvc.dll,PcaPatchSdbTask'
filter_main_azure_managed:
    SourceHostname|endswith: '.internal.cloudapp.net'
filter_main_svchost_update_processes:
    # Note: This require "ParentImage" data enrichment.
    ParentImage: 'C:\Windows\System32\svchost.exe'
    DestinationPort: 443
condition: selection and not 1 of filter_main_*

False positives (as the rule lists them)

  • Communication to other corporate systems that use IP addresses from public address spaces

Tags

  • attack.stealth
  • attack.t1218.011
  • attack.execution

MITRE ATT&CK ids this rule names

References

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_rundll32_net_connections.yml

Sources and licences

  • SigmaHQ

    "Rundll32 Internet Connection" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/network_connection/net_connection_win_rundll32_net_connections.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: Rundll32 Internet Connection",
entity page, dataset version ref-ccaf19063764, updated 2024-03-13T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/cdc8da7d-c303-42f8-b08c-b4ab47230263 (accessed 2026-11-03).
Underlying source: SigmaHQ rule cdc8da7d-c303-42f8-b08c-b4ab47230263, 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.