Microsoft IIS Connection Strings Decryption

 1[metadata]
 2creation_date = "2020/08/18"
 3integration = ["endpoint", "windows", "system"]
 4maturity = "production"
 5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
 6min_stack_version = "8.3.0"
 7updated_date = "2024/03/28"
 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.process-*", "logs-windows.*", "endgame-*", "logs-system.security*"]
18language = "eql"
19license = "Elastic License v2"
20max_signals = 33
21name = "Microsoft IIS Connection Strings Decryption"
22references = [
23    "https://blog.netspi.com/decrypting-iis-passwords-to-break-out-of-the-dmz-part-1/",
24    "https://symantec-enterprise-blogs.security.com/blogs/threat-intelligence/greenbug-espionage-telco-south-asia",
25]
26risk_score = 73
27rule_id = "c25e9c87-95e1-4368-bfab-9fd34cf867ec"
28setup = """## Setup
29
30If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
31events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
32Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
33`event.ingested` to @timestamp.
34For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
35"""
36severity = "high"
37tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Credential Access", "Data Source: Elastic Endgame", "Data Source: Elastic Defend"]
38timestamp_override = "event.ingested"
39type = "eql"
40
41query = '''
42process where host.os.type == "windows" and event.type == "start" and
43  (process.name : "aspnet_regiis.exe" or ?process.pe.original_file_name == "aspnet_regiis.exe") and
44  process.args : "connectionStrings" and process.args : "-pdf"
45'''
46
47
48[[rule.threat]]
49framework = "MITRE ATT&CK"
50[[rule.threat.technique]]
51id = "T1003"
52name = "OS Credential Dumping"
53reference = "https://attack.mitre.org/techniques/T1003/"
54
55
56[rule.threat.tactic]
57id = "TA0006"
58name = "Credential Access"
59reference = "https://attack.mitre.org/tactics/TA0006/"