Unusual Network Connection via RunDLL32

Elastic Stack Serverless Security

Identifies unusual instances of rundll32.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: None

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Defense Evasion

version: 10

Rule authors:

• Elastic

Rule license: Elastic License v2

sequence by host.id, process.entity_id with maxspan=1m
  [process where event.type in ("start", "process_started") and process.name : "rundll32.exe" and process.args_count == 1]
  [network where process.name : "rundll32.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")]

Framework: MITRE ATT&CKTM

• 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/

• Sub-technique:

  • Name: Rundll32
  • ID: T1218.011
  • Reference URL: https://attack.mitre.org/techniques/T1218/011/