Unusual Child Process of dns.exe

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.

Triage 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.

Framework: MITRE ATT&CK^TM