Suspicious .NET Code Compilation

Elastic Stack Serverless Security

Identifies suspicious .NET code execution connections.

Rule type: eql

Rule indices:

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

Severity: medium

Risk score: 47

Runs every: 5m

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: None

Tags:

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

Version: 6

Rule authors:

• Elastic

Rule license: Elastic License v2

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate event.ingested to @timestamp for this rule to work.

process where event.type in ("start", "process_started") and
  process.name : ("csc.exe", "vbc.exe") and
  process.parent.name : ("wscript.exe", "mshta.exe", "cscript.exe", "wmic.exe", "svchost.exe", "rundll32.exe", "cmstp.exe", "regsvr32.exe")

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Defense Evasion
  • ID: TA0005
  • Reference URL: https://attack.mitre.org/tactics/TA0005/

• Technique:

  • Name: Obfuscated Files or Information
  • ID: T1027
  • Reference URL: https://attack.mitre.org/techniques/T1027/

• Sub-technique:

  • Name: Compile After Delivery
  • ID: T1027.004
  • Reference URL: https://attack.mitre.org/techniques/T1027/004/