Disabling User Account Control via Registry Modification

  1[metadata]
  2creation_date = "2021/01/20"
  3integration = ["endpoint", "windows", "m365_defender", "sentinel_one_cloud_funnel"]
  4maturity = "production"
  5updated_date = "2024/10/15"
  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 = """
 12User Account Control (UAC) can help mitigate the impact of malware on Windows hosts. With UAC, apps and tasks always run
 13in the security context of a non-administrator account, unless an administrator specifically authorizes
 14administrator-level access to the system. This rule identifies registry value changes to bypass User Access Control
 15(UAC) protection.
 16"""
 17from = "now-9m"
 18index = ["winlogbeat-*", "logs-endpoint.events.registry-*", "logs-windows.sysmon_operational-*", "endgame-*", "logs-m365_defender.event-*", "logs-sentinel_one_cloud_funnel.*"]
 19language = "eql"
 20license = "Elastic License v2"
 21name = "Disabling User Account Control via Registry Modification"
 22note = """## Triage and analysis
 23
 24### Investigating Disabling User Account Control via Registry Modification
 25
 26Windows User Account Control (UAC) allows a program to elevate its privileges (tracked as low to high integrity levels) to perform a task under administrator-level permissions, possibly by prompting the user for confirmation. UAC can deny an operation under high-integrity enforcement, or allow the user to perform the action if they are in the local administrators group and enter an administrator password when prompted.
 27
 28For more information about the UAC and how it works, check the [official Microsoft docs page](https://docs.microsoft.com/en-us/windows/security/identity-protection/user-account-control/how-user-account-control-works).
 29
 30Attackers may disable UAC to execute code directly in high integrity. This rule identifies registry value changes to bypass the UAC protection.
 31
 32#### Possible investigation steps
 33
 34- 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.
 35- Investigate other alerts associated with the user/host during the past 48 hours.
 36- Inspect the host for suspicious or abnormal behaviors in the alert timeframe.
 37- Investigate abnormal behaviors observed by the subject process such as network connections, registry or file modifications, and any spawned child processes.
 38- Analyze non-system processes executed with high integrity after UAC was disabled for unknown or suspicious processes.
 39- Retrieve the suspicious processes' executables and determine if they are malicious:
 40  - Use a private sandboxed malware analysis system to perform analysis.
 41    - Observe and collect information about the following activities:
 42      - Attempts to contact external domains and addresses.
 43      - File and registry access, modification, and creation activities.
 44      - Service creation and launch activities.
 45      - Scheduled tasks creation.
 46  - Use the PowerShell `Get-FileHash` cmdlet to get the files' SHA-256 hash values.
 47    - Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
 48
 49### False positive analysis
 50
 51- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.
 52
 53### Response and remediation
 54
 55- Initiate the incident response process based on the outcome of the triage.
 56- Isolate the involved host to prevent further post-compromise behavior.
 57- If the triage identified malware, search the environment for additional compromised hosts.
 58  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 59  - Stop suspicious processes.
 60  - Immediately block the identified indicators of compromise (IoCs).
 61  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
 62- Remove and block malicious artifacts identified during triage.
 63- Restore UAC settings to the desired state.
 64- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 65- 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.
 66- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 67- 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).
 68"""
 69references = [
 70    "https://www.greyhathacker.net/?p=796",
 71    "https://docs.microsoft.com/en-us/windows/security/identity-protection/user-account-control/user-account-control-group-policy-and-registry-key-settings",
 72    "https://docs.microsoft.com/en-us/windows/security/identity-protection/user-account-control/user-account-control-overview",
 73    "https://www.elastic.co/security-labs/dissecting-remcos-rat-part-four",
 74]
 75risk_score = 47
 76rule_id = "d31f183a-e5b1-451b-8534-ba62bca0b404"
 77severity = "medium"
 78tags = [
 79    "Domain: Endpoint",
 80    "OS: Windows",
 81    "Use Case: Threat Detection",
 82    "Tactic: Privilege Escalation",
 83    "Resources: Investigation Guide",
 84    "Data Source: Elastic Endgame",
 85    "Data Source: Elastic Defend",
 86    "Data Source: Sysmon",
 87    "Data Source: Microsoft Defender for Endpoint",
 88    "Data Source: SentinelOne",
 89]
 90timestamp_override = "event.ingested"
 91type = "eql"
 92
 93query = '''
 94registry where host.os.type == "windows" and event.type == "change" and
 95  registry.path :
 96    (
 97      "HKLM\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\EnableLUA",
 98      "HKLM\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\ConsentPromptBehaviorAdmin",
 99      "HKLM\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\PromptOnSecureDesktop",
100      "\\REGISTRY\\MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\EnableLUA",
101      "\\REGISTRY\\MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\ConsentPromptBehaviorAdmin",
102      "\\REGISTRY\\MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\PromptOnSecureDesktop",
103      "MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\EnableLUA",
104      "MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\ConsentPromptBehaviorAdmin",
105      "MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\PromptOnSecureDesktop"
106    ) and
107  registry.data.strings : ("0", "0x00000000")
108'''
109
110
111[[rule.threat]]
112framework = "MITRE ATT&CK"
113[[rule.threat.technique]]
114id = "T1548"
115name = "Abuse Elevation Control Mechanism"
116reference = "https://attack.mitre.org/techniques/T1548/"
117[[rule.threat.technique.subtechnique]]
118id = "T1548.002"
119name = "Bypass User Account Control"
120reference = "https://attack.mitre.org/techniques/T1548/002/"
121
122
123
124[rule.threat.tactic]
125id = "TA0004"
126name = "Privilege Escalation"
127reference = "https://attack.mitre.org/tactics/TA0004/"
128[[rule.threat]]
129framework = "MITRE ATT&CK"
130[[rule.threat.technique]]
131id = "T1112"
132name = "Modify Registry"
133reference = "https://attack.mitre.org/techniques/T1112/"
134
135[[rule.threat.technique]]
136id = "T1548"
137name = "Abuse Elevation Control Mechanism"
138reference = "https://attack.mitre.org/techniques/T1548/"
139[[rule.threat.technique.subtechnique]]
140id = "T1548.002"
141name = "Bypass User Account Control"
142reference = "https://attack.mitre.org/techniques/T1548/002/"
143
144
145[[rule.threat.technique]]
146id = "T1562"
147name = "Impair Defenses"
148reference = "https://attack.mitre.org/techniques/T1562/"
149[[rule.threat.technique.subtechnique]]
150id = "T1562.001"
151name = "Disable or Modify Tools"
152reference = "https://attack.mitre.org/techniques/T1562/001/"
153
154
155
156[rule.threat.tactic]
157id = "TA0005"
158name = "Defense Evasion"
159reference = "https://attack.mitre.org/tactics/TA0005/"