Unusual Child Process of dns.exe
editUnusual Child Process of dns.exe
editIdentifies 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: eql
Rule indices:
- winlogbeat-*
- logs-endpoint.events.*
- logs-windows.*
Severity: high
Risk score: 73
Runs every: 5 minutes
Searches indices from: now-9m (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://github.com/maxpl0it/CVE-2020-1350-DoS
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Initial Access
Version: 5 (version history)
Added (Elastic Stack release): 7.10.0
Last modified (Elastic Stack release): 7.13.0
Rule authors: Elastic
Rule license: Elastic License v2
Potential false positives
editWerfault.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
editTriage and analysis
nvestigating Unusual Child Process 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
editprocess where event.type == "start" and process.parent.name : "dns.exe" and not process.name : "conhost.exe"
Threat mapping
editFramework: 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/
Rule version history
edit- Version 5 (7.13.0 release)
-
-
Updated query, changed from:
event.category:process and event.type:start and process.parent.name:dns.exe and not process.name:conhost.exe
-
- Version 4 (7.12.0 release)
-
- Formatting only
- Version 3 (7.11.2 release)
-
- Formatting only
- Version 2 (7.11.0 release)
-
- Formatting only