Unusual Network Connection via DllHost

Identifies unusual instances of dllhost.exe making outbound network connections. This may indicate adversarial Command and Control activity.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.*
logs-windows.*

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

References:

Tags:

Elastic
Host
Windows
Threat Detection
Defense Evasion

Version: 1

Added (Elastic Stack release): 7.14.0

Rule authors: Elastic

Rule license: Elastic License v2

Rule query

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sequence by host.id, process.entity_id with maxspan=1m [process
where event.type in ("start", "process_started") and process.name :
"dllhost.exe" and process.args_count == 1] [network where
process.name : "dllhost.exe" and not cidrmatch(destination.ip,
"10.0.0.0/8", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12",
"192.0.0.0/24", "192.0.0.0/29", "192.0.0.8/32", "192.0.0.9/32",
"192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24",
"192.31.196.0/24", "192.52.193.0/24", "192.168.0.0/16",
"192.88.99.0/24", "224.0.0.0/4", "100.64.0.0/10",
"192.175.48.0/24", "198.18.0.0/15", "198.51.100.0/24",
"203.0.113.0/24", "240.0.0.0/4", "::1", "FE80::/10", "FF00::/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/

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