Code Signing Policy Modification Through Registry

  1[metadata]
  2creation_date = "2023/01/31"
  3integration = ["endpoint", "windows"]
  4maturity = "production"
  5updated_date = "2024/05/21"
  6
  7[transform]
  8[[transform.osquery]]
  9label = "Osquery - Retrieve All Non-Microsoft Drivers with Virustotal Link"
 10query = """
 11SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, class, description, directory, image,
 12issuer_name, manufacturer, service, signed, subject_name FROM drivers JOIN authenticode ON drivers.image =
 13authenticode.path JOIN hash ON drivers.image = hash.path WHERE NOT (provider == "Microsoft" AND signed == "1")
 14"""
 15
 16[[transform.osquery]]
 17label = "Osquery - Retrieve All Unsigned Drivers with Virustotal Link"
 18query = """
 19SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, class, description, directory, image,
 20issuer_name, manufacturer, service, signed, subject_name FROM drivers JOIN authenticode ON drivers.image =
 21authenticode.path JOIN hash ON drivers.image = hash.path WHERE signed == "0"
 22"""
 23
 24
 25[rule]
 26author = ["Elastic"]
 27description = """
 28Identifies attempts to disable the code signing policy through the registry. Code signing provides authenticity on a
 29program, and grants the user with the ability to check whether the program has been tampered with. By allowing the
 30execution of unsigned or self-signed code, threat actors can craft and execute malicious code.
 31"""
 32from = "now-9m"
 33index = ["winlogbeat-*", "logs-endpoint.events.registry-*", "logs-windows.sysmon_operational-*", "endgame-*"]
 34language = "eql"
 35license = "Elastic License v2"
 36name = "Code Signing Policy Modification Through Registry"
 37note = """## Triage and analysis
 38
 39### Investigating Code Signing Policy Modification Through Registry
 40
 41Microsoft created the Windows Driver Signature Enforcement (DSE) security feature to prevent drivers with invalid signatures from loading and executing into the kernel (ring 0). DSE aims to protect systems by blocking attackers from loading malicious drivers on targets. 
 42
 43This protection is essential for maintaining system security. However, attackers or administrators can disable DSE and load untrusted drivers, which can put the system at risk. Therefore, it's important to keep this feature enabled and only load drivers from trusted sources to ensure system integrity and security.
 44
 45This rule identifies registry modifications that can disable DSE.
 46
 47> **Note**:
 48> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/master/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 49
 50#### Possible investigation steps
 51
 52- Identify the user account that performed the action and whether it should perform this kind of action.
 53- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
 54- Investigate other alerts associated with the user/host during the past 48 hours.
 55- Use Osquery and endpoint driver events (`event.category = "driver"`) to investigate if suspicious drivers were loaded into the system after the registry was modified.
 56  - $osquery_0
 57  - $osquery_1
 58- Identify the driver's `Device Name` and `Service Name`.
 59- Check for alerts from the rules specified in the `Related Rules` section.
 60
 61### False positive analysis
 62
 63- This activity should not happen legitimately. The security team should address any potential benign true positive (B-TP), as this configuration can put the user and the domain at risk.
 64
 65### Related Rules
 66
 67- First Time Seen Driver Loaded - df0fd41e-5590-4965-ad5e-cd079ec22fa9
 68- Untrusted Driver Loaded - d8ab1ec1-feeb-48b9-89e7-c12e189448aa
 69- Code Signing Policy Modification Through Built-in tools - b43570de-a908-4f7f-8bdb-b2df6ffd8c80
 70
 71### Response and remediation
 72
 73- Initiate the incident response process based on the outcome of the triage.
 74- Isolate the involved host to prevent further post-compromise behavior.
 75- Disable and uninstall all suspicious drivers found in the system. This can be done via Device Manager. (Note that this step may require you to boot the system into Safe Mode.)
 76- Remove the related services and registry keys found in the system. Note that the service will probably not stop if the driver is still installed.
 77  - This can be done via PowerShell `Remove-Service` cmdlet.
 78- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 79- Remove and block malicious artifacts identified during triage.
 80- Ensure that the Driver Signature Enforcement is enabled on the system.
 81- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
 82- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 83- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
 84"""
 85risk_score = 47
 86rule_id = "da7733b1-fe08-487e-b536-0a04c6d8b0cd"
 87severity = "medium"
 88tags = [
 89    "Domain: Endpoint",
 90    "OS: Windows",
 91    "Use Case: Threat Detection",
 92    "Tactic: Defense Evasion",
 93    "Data Source: Elastic Endgame",
 94    "Resources: Investigation Guide",
 95    "Data Source: Elastic Defend",
 96    "Data Source: Sysmon",
 97]
 98timestamp_override = "event.ingested"
 99type = "eql"
100
101query = '''
102registry where host.os.type == "windows" and event.type : ("creation", "change") and
103(
104  registry.path : (
105    "HKEY_USERS\\*\\Software\\Policies\\Microsoft\\Windows NT\\Driver Signing\\BehaviorOnFailedVerify",
106    "HKU\\*\\Software\\Policies\\Microsoft\\Windows NT\\Driver Signing\\BehaviorOnFailedVerify",
107    "\\REGISTRY\\USER\\*\\Software\\Policies\\Microsoft\\Windows NT\\Driver Signing\\BehaviorOnFailedVerify"
108  ) and
109  registry.value: "BehaviorOnFailedVerify" and
110  registry.data.strings : ("0", "0x00000000", "1", "0x00000001")
111)
112'''
113
114
115[[rule.threat]]
116framework = "MITRE ATT&CK"
117[[rule.threat.technique]]
118id = "T1112"
119name = "Modify Registry"
120reference = "https://attack.mitre.org/techniques/T1112/"
121
122[[rule.threat.technique]]
123id = "T1553"
124name = "Subvert Trust Controls"
125reference = "https://attack.mitre.org/techniques/T1553/"
126[[rule.threat.technique.subtechnique]]
127id = "T1553.006"
128name = "Code Signing Policy Modification"
129reference = "https://attack.mitre.org/techniques/T1553/006/"
130
131
132
133[rule.threat.tactic]
134id = "TA0005"
135name = "Defense Evasion"
136reference = "https://attack.mitre.org/tactics/TA0005/"