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Elastic Docs ›Elastic Security Solution [7.11] ›Detections and Alerts ›Prebuilt rule reference

Unusual File Modification by dns.exe

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Unusual File Modification by dns.exe

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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: query

Rule indices:

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

Severity: high

Risk score: 73

Runs every: 5 minutes

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Execution

Version: 3 (version history)

Added (Elastic Stack release): 7.10.0

Last modified (Elastic Stack release): 7.11.2

Rule authors: Elastic

Rule license: Elastic License

Investigation guide

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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.

Rule query

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event.category:file and process.name:dns.exe and event.type:(creation
or deletion or change) and not file.name:dns.log

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 3 (7.11.2 release)
  • Formatting only
Version 2 (7.11.0 release)

  • Updated query, changed from:

    event.category:file and process.name:dns.exe and not file.name:dns.log
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