IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

« Unusual Network Activity from a Windows System Binary Unusual Network Destination Domain Name »

› › ›

Unusual Network Connection via RunDLL32

edit

IMPORTANT: This documentation is no longer updated. Refer to Elastic's version policy and the latest documentation.

Unusual Network Connection via RunDLL32

edit

Identifies unusual instances of rundll32.exe making outbound network connections. This may indicate adversarial activity and may identify malicious DLLs.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

Tags:

Elastic
Host
Windows
Threat Detection
Execution

Version: 7 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.11.0

Rule authors: Elastic

Rule license: Elastic License

Rule query

edit

sequence by host.id, process.entity_id with maxspan=1m [process
where event.type in ("start", "process_started", "info") and
process.name : "rundll32.exe" and process.args_count == 1] [network
where process.name : "rundll32.exe" and network.protocol != "dns" and
network.direction == "outgoing" and not cidrmatch(destination.ip,
"10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16", "127.0.0.0/8")]

Threat mapping

edit

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Signed Binary Proxy Execution
- ID: T1218
- Reference URL: https://attack.mitre.org/techniques/T1218/

Rule version history

edit

Version 7 (7.11.0 release)

Updated query, changed from:

sequence by process.entity_id [process where process.name :
"rundll32.exe" and event.type == "start"] [network where
process.name : "rundll32.exe" and not cidrmatch(destination.ip,
"10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16", "127.0.0.0/8")]

Version 6 (7.10.0 release)

Updated query, changed from:

event.category:network and event.type:connection and
process.name:rundll32.exe and not destination.ip:(10.0.0.0/8 or
172.16.0.0/12 or 192.168.0.0/16 or 127.0.0.0/8)

Version 5 (7.9.1 release)

Formatting only

Version 4 (7.9.0 release)

Updated query, changed from:

process.name:rundll32.exe and event.action:"Network connection
detected (rule: NetworkConnect)" and not destination.ip:(10.0.0.0/8 or
172.16.0.0/12 or 192.168.0.0/16 or 127.0.0.0/8)

Version 3 (7.8.0 release)

Updated query, changed from:

process.name:rundll32.exe and event.action:"Network connection
detected (rule: NetworkConnect)" and not destination.ip:(10.0.0.0/8 or
172.16.0.0/12 or 192.168.0.0/16)

Version 2 (7.7.0 release)

Updated query, changed from:

process.name:rundll32.exe and event.action:"Network connection
detected (rule: NetworkConnect)" and not destination.ip:10.0.0.0/8 and
not destination.ip:172.16.0.0/12 and not destination.ip:192.168.0.0/16

« Unusual Network Activity from a Windows System Binary Unusual Network Destination Domain Name »