Unusual File Modification by dns.exe

Elastic Stack Serverless Security

Identifies an unexpected file being modified by dns.exe, the process responsible for Windows DNS Server services, which may indicate activity related to remote code execution or other forms of exploitation.

Rule type: eql

Rule indices:

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

Severity: high

Risk score: 73

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:

• https://research.checkpoint.com/2020/resolving-your-way-into-domain-admin-exploiting-a-17-year-old-bug-in-windows-dns-servers/
• https://msrc-blog.microsoft.com/2020/07/14/july-2020-security-update-cve-2020-1350-vulnerability-in-windows-domain-name-system-dns-server/
• https://www.elastic.co/security-labs/detection-rules-for-sigred-vulnerability

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Initial Access

Version: 101

Rule authors:

• Elastic

Rule license: Elastic License v2

Detection alerts from this rule indicate potential unusual/abnormal file writes from the DNS Server service process (dns.exe) after exploitation from CVE-2020-1350 (SigRed) has occurred. Here are some possible avenues of investigation:

• Post-exploitation, adversaries may write additional files or payloads to the system as additional discovery/exploitation/persistence mechanisms.
• Any suspicious or abnormal files written from dns.exe should be reviewed and investigated with care.

file where process.name : "dns.exe" and event.type in ("creation", "deletion", "change") and
  not file.name : "dns.log"

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Initial Access
  • ID: TA0001
  • Reference URL: https://attack.mitre.org/tactics/TA0001/

• Technique:

  • Name: External Remote Services
  • ID: T1133
  • Reference URL: https://attack.mitre.org/techniques/T1133/