Unusual File Modification by dns.exe
editUnusual File Modification by dns.exe
editIdentifies 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.sysmon_operational-*
- endgame-*
Severity: high
Risk score: 73
Runs every: 5m
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://www.elastic.co/security-labs/detection-rules-for-sigred-vulnerability
Tags:
- Domain: Endpoint
- OS: Windows
- Use Case: Threat Detection
- Tactic: Lateral Movement
- Data Source: Elastic Endgame
- Use Case: Vulnerability
- Data Source: Elastic Defend
- Data Source: Sysmon
Version: 109
Rule authors:
- Elastic
Rule license: Elastic License v2
Investigation guide
editTriage and analysis
Investigating Unusual File Write
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.
Setup
editSetup
If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
events will not define event.ingested
and default fallback for EQL rules was not added until version 8.2.
Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
event.ingested
to @timestamp.
For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
Rule query
editfile where host.os.type == "windows" and process.name : "dns.exe" and event.type in ("creation", "deletion", "change") and not file.name : "dns.log" and not (file.extension : ("old", "temp", "bak", "dns", "arpa") and file.path : "C:\\Windows\\System32\\dns\\*")
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Lateral Movement
- ID: TA0008
- Reference URL: https://attack.mitre.org/tactics/TA0008/
-
Technique:
- Name: Exploitation of Remote Services
- ID: T1210
- Reference URL: https://attack.mitre.org/techniques/T1210/