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Elastic Docs ›Elastic Security Solution [7.10] ›Detections and Alerts ›Prebuilt rule reference

Unusual Child Process of dns.exe

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Unusual Child Process of dns.exe

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Identifies an unexpected process spawning from 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: 1

Added (Elastic Stack release): 7.10.0

Rule authors: Elastic

Rule license: Elastic License

Potential false positives

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Werfault.exe will legitimately spawn when dns.exe crashes, but the DNS service is very stable and so this is a low occurring event. Denial of Service (DoS) attempts by intentionally crashing the service will also cause werfault.exe to spawn.

Investigation guide

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Detection alerts from this rule indicate potential suspicious child processes spawned after exploitation from CVE-2020-1350 (SigRed) has occurred. Here are some possible avenues of investigation:

  • Any suspicious or abnormal child process spawned from dns.exe should be reviewed and investigated with care. It’s impossible to predict what an adversary may deploy as the follow-on process after the exploit, but built-in discovery/enumeration utilities should be top of mind (whoami.exe, netstat.exe, systeminfo.exe, tasklist.exe).
  • Built-in Windows programs that contain capabilities used to download and execute additional payloads should also be considered. This is not an exhaustive list, but ideal candidates to start out would be: mshta.exe, powershell.exe, regsvr32.exe, rundll32.exe, wscript.exe, wmic.exe.
  • If the DoS exploit is successful and DNS Server service crashes, be mindful of potential child processes related to werfault.exe occurring.
  • Any subsequent activity following the child process spawned related to execution/network activity should be thoroughly reviewed from the endpoint.

Rule query

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event.category:process and event.type:start and
process.parent.name:dns.exe and not process.name:conhost.exe

Threat mapping

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Framework: MITRE ATT&CKTM

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