Microsoft IIS Connection Strings Decryption

 1[metadata]
 2creation_date = "2020/08/18"
 3integration = ["endpoint", "windows", "system", "m365_defender", "sentinel_one_cloud_funnel", "crowdstrike"]
 4maturity = "production"
 5updated_date = "2024/11/02"
 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 use of aspnet_regiis to decrypt Microsoft IIS connection strings. An attacker with Microsoft IIS web server
13access via a webshell or alike can decrypt and dump any hardcoded connection strings, such as the MSSQL service account
14password using aspnet_regiis command.
15"""
16from = "now-9m"
17index = [
18    "winlogbeat-*",
19    "logs-endpoint.events.process-*",
20    "logs-windows.forwarded*",
21    "logs-windows.sysmon_operational-*",
22    "endgame-*",
23    "logs-system.security*",
24    "logs-m365_defender.event-*",
25    "logs-sentinel_one_cloud_funnel.*",
26    "logs-crowdstrike.fdr*",
27]
28language = "eql"
29license = "Elastic License v2"
30max_signals = 33
31name = "Microsoft IIS Connection Strings Decryption"
32references = [
33    "https://blog.netspi.com/decrypting-iis-passwords-to-break-out-of-the-dmz-part-1/",
34    "https://symantec-enterprise-blogs.security.com/blogs/threat-intelligence/greenbug-espionage-telco-south-asia",
35]
36risk_score = 73
37rule_id = "c25e9c87-95e1-4368-bfab-9fd34cf867ec"
38severity = "high"
39tags = [
40    "Domain: Endpoint",
41    "OS: Windows",
42    "Use Case: Threat Detection",
43    "Tactic: Credential Access",
44    "Data Source: Elastic Endgame",
45    "Data Source: Elastic Defend",
46    "Data Source: System",
47    "Data Source: Microsoft Defender for Endpoint",
48    "Data Source: Sysmon",
49    "Data Source: SentinelOne",
50    "Data Source: Crowdstrike",
51]
52timestamp_override = "event.ingested"
53type = "eql"
54
55query = '''
56process where host.os.type == "windows" and event.type == "start" and
57  (process.name : "aspnet_regiis.exe" or ?process.pe.original_file_name == "aspnet_regiis.exe") and
58  process.args : "connectionStrings" and process.args : "-pdf"
59'''
60
61
62[[rule.threat]]
63framework = "MITRE ATT&CK"
64[[rule.threat.technique]]
65id = "T1003"
66name = "OS Credential Dumping"
67reference = "https://attack.mitre.org/techniques/T1003/"
68
69
70[rule.threat.tactic]
71id = "TA0006"
72name = "Credential Access"
73reference = "https://attack.mitre.org/tactics/TA0006/"