Unusual File Modification by dns.exe

 1[metadata]
 2creation_date = "2020/07/16"
 3integration = ["endpoint", "windows"]
 4maturity = "production"
 5updated_date = "2025/01/17"
 6min_stack_version = "8.14.0"
 7min_stack_comments = "Breaking change at 8.14.0 for the Windows Integration."
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Identifies an unexpected file being modified by dns.exe, the process responsible for Windows DNS Server services, which
13may indicate activity related to remote code execution or other forms of exploitation.
14"""
15from = "now-9m"
16index = ["winlogbeat-*", "logs-endpoint.events.file-*", "logs-windows.sysmon_operational-*", "endgame-*"]
17language = "eql"
18license = "Elastic License v2"
19name = "Unusual File Modification by dns.exe"
20note = """## Triage and analysis
21
22### Investigating Unusual File Modification by dns.exe
23Detection 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:
24- Post-exploitation, adversaries may write additional files or payloads to the system as additional discovery/exploitation/persistence mechanisms.
25- Any suspicious or abnormal files written from `dns.exe` should be reviewed and investigated with care.
26"""
27references = [
28    "https://research.checkpoint.com/2020/resolving-your-way-into-domain-admin-exploiting-a-17-year-old-bug-in-windows-dns-servers/",
29    "https://msrc-blog.microsoft.com/2020/07/14/july-2020-security-update-cve-2020-1350-vulnerability-in-windows-domain-name-system-dns-server/",
30    "https://www.elastic.co/security-labs/detection-rules-for-sigred-vulnerability",
31]
32risk_score = 73
33rule_id = "c7ce36c0-32ff-4f9a-bfc2-dcb242bf99f9"
34severity = "high"
35tags = [
36    "Domain: Endpoint",
37    "OS: Windows",
38    "Use Case: Threat Detection",
39    "Tactic: Lateral Movement",
40    "Data Source: Elastic Endgame",
41    "Use Case: Vulnerability",
42    "Data Source: Elastic Defend",
43    "Data Source: Sysmon",
44    "Resources: Investigation Guide",
45]
46timestamp_override = "event.ingested"
47type = "eql"
48
49query = '''
50file where host.os.type == "windows" and process.name : "dns.exe" and event.type in ("creation", "deletion", "change") and
51  not file.name : "dns.log" and not
52  (file.extension : ("old", "temp", "bak", "dns", "arpa") and file.path : "C:\\Windows\\System32\\dns\\*") and
53
54  /* DNS logs with custom names, header converts to "DNS Server log" */
55  not ?file.Ext.header_bytes : "444e5320536572766572206c6f67*"
56'''
57
58
59[[rule.threat]]
60framework = "MITRE ATT&CK"
61[[rule.threat.technique]]
62id = "T1210"
63name = "Exploitation of Remote Services"
64reference = "https://attack.mitre.org/techniques/T1210/"
65
66
67[rule.threat.tactic]
68id = "TA0008"
69name = "Lateral Movement"
70reference = "https://attack.mitre.org/tactics/TA0008/"