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

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Unusual Network Connection via RunDLL32

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Unusual Network Connection via RunDLL32

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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

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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

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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

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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

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