Microsoft IIS Connection Strings Decryption

 1[metadata]
 2creation_date = "2020/08/18"
 3integration = ["endpoint", "windows"]
 4maturity = "production"
 5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
 6min_stack_version = "8.3.0"
 7updated_date = "2023/06/22"
 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 = ["winlogbeat-*", "logs-endpoint.events.*", "logs-windows.*", "endgame-*"]
18language = "eql"
19license = "Elastic License v2"
20max_signals = 33
21name = "Microsoft IIS Connection Strings Decryption"
22note = """## Setup
23
24If 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 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.
25"""
26references = [
27    "https://blog.netspi.com/decrypting-iis-passwords-to-break-out-of-the-dmz-part-1/",
28    "https://symantec-enterprise-blogs.security.com/blogs/threat-intelligence/greenbug-espionage-telco-south-asia",
29]
30risk_score = 73
31rule_id = "c25e9c87-95e1-4368-bfab-9fd34cf867ec"
32severity = "high"
33tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Credential Access", "Data Source: Elastic Endgame", "Data Source: Elastic Defend"]
34timestamp_override = "event.ingested"
35type = "eql"
36
37query = '''
38process where host.os.type == "windows" and event.type == "start" and
39  (process.name : "aspnet_regiis.exe" or process.pe.original_file_name == "aspnet_regiis.exe") and
40  process.args : "connectionStrings" and process.args : "-pdf"
41'''
42
43
44[[rule.threat]]
45framework = "MITRE ATT&CK"
46[[rule.threat.technique]]
47id = "T1003"
48name = "OS Credential Dumping"
49reference = "https://attack.mitre.org/techniques/T1003/"
50
51
52[rule.threat.tactic]
53id = "TA0006"
54name = "Credential Access"
55reference = "https://attack.mitre.org/tactics/TA0006/"