Execution via Windows Command Debugging Utility

An adversary can use the Windows command line debugging utility cdb.exe to execute commands or shellcode. This rule looks for those instances and where the cdb.exe binary is outside of the normal WindowsKit installation paths.

Rule type: eql

Rule indices:

logs-endpoint.events.process-*
logs-windows.sysmon_operational-*
endgame-*
logs-sentinel_one_cloud_funnel.*
logs-m365_defender.event-*
logs-system.security-*

Severity: medium

Risk score: 47

Runs every: 5m

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

Maximum alerts per execution: 100

References:

https://lolbas-project.github.io/lolbas/OtherMSBinaries/Cdb/

Tags:

Domain: Endpoint
OS: Windows
Use Case: Threat Detection
Tactic: Defense Evasion
Data Source: Elastic Endgame
Data Source: Elastic Defend
Data Source: Sysmon
Data Source: SentinelOne
Data Source: Microsoft Defender for Endpoint

Version: 101

Rule authors:

Elastic

Rule license: Elastic License v2

Setup

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Setup

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 version 8.2. Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate event.ingested to @timestamp. For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html

Rule query

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process where host.os.type == "windows" and event.type == "start" and
 (?process.pe.original_file_name == "CDB.Exe" or process.name : "cdb.exe") and
  process.args : ("-cf", "-c", "-pd") and
  not process.executable : ("?:\\Program Files (x86)\\*\\cdb.exe", "?:\\Program Files\\*\\cdb.exe")

Framework: MITRE ATT&CK^TM

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

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