Detection: Windows UAC Bypass Suspicious Escalation Behavior

Updated Date: 2024-11-28 ID: 00d050d3-a5b4-4565-a6a5-a31f69681dc3 Author: Steven Dick Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects when a process spawns an executable known for User Account Control (UAC) bypass exploitation and subsequently monitors for any child processes with a higher integrity level than the original process. This detection leverages Sysmon EventID 1 data, focusing on process integrity levels and known UAC bypass executables. This activity is significant as it may indicate an attacker has successfully used a UAC bypass exploit to escalate privileges. If confirmed malicious, the attacker could gain elevated privileges, potentially leading to further system compromise and persistent access.

 1
 2| tstats `security_content_summariesonly` count max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_integrity_level IN ("low","medium") by Processes.dest, Processes.user, Processes.process_name, Processes.process, Processes.process_guid, Processes.process_path, Processes.process_integrity_level, Processes.process_current_directory 
 3| `drop_dm_object_name(Processes)` 
 4| eval original_integrity_level = CASE(match(process_integrity_level,"low"),1,match(process_integrity_level,"medium"),2,match(process_integrity_level,"high"),3,match(process_integrity_level,"system"),4,true(),0) 
 5| rename process_guid as join_guid_1, process* as parent_process* 
 6| join max=0 dest join_guid_1 [
 7| tstats `security_content_summariesonly` count min(_time) as firstTime from datamodel=Endpoint.Processes where Processes.process_integrity_level IN ("high","system") AND Processes.process_name IN (`uacbypass_process_name`) by Processes.dest, Processes.parent_process_guid, Processes.process_name, Processes.process_guid 
 8| `drop_dm_object_name(Processes)` 
 9| rename parent_process_guid as join_guid_1, process_guid as join_guid_2, process_name as uac_process_name ] 
10| join max=0 dest join_guid_2 [
11| tstats `security_content_summariesonly` count min(_time) as firstTime from datamodel=Endpoint.Processes where Processes.parent_process_name IN (`uacbypass_process_name`) AND Processes.process_integrity_level IN ("high","system") by Processes.dest, Processes.parent_process_guid, Processes.process_name, Processes.process, Processes.process_guid, Processes.process_path, Processes.process_integrity_level, Processes.process_current_directory 
12| `drop_dm_object_name(Processes)` 
13| rename parent_process_guid as join_guid_2 
14| eval elevated_integrity_level = CASE(match(process_integrity_level,"low"),1,match(process_integrity_level,"medium"),2,match(process_integrity_level,"high"),3,match(process_integrity_level,"system"),4,true(),0)] 
15| where elevated_integrity_level > original_integrity_level 
16| table dest user parent_process parent_process_name parent_process_integrity_level process_integrity_level process process_name uac_process_name count firstTime lastTime 
17| `security_content_ctime(firstTime)` 
18| `security_content_ctime(lastTime)` 
19| `windows_uac_bypass_suspicious_escalation_behavior_filter`

Data Source

Name Platform Sourcetype Source
CrowdStrike ProcessRollup2 N/A 'crowdstrike:events:sensor' 'crowdstrike'
Sysmon EventID 1 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Security'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_uac_bypass_suspicious_escalation_behavior_filter search *
windows_uac_bypass_suspicious_escalation_behavior_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1548 Abuse Elevation Control Mechanism Defense Evasion
T1548.002 Bypass User Account Control Privilege Escalation
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10
APT29
APT37
BRONZE BUTLER
Cobalt Group
Earth Lusca
Evilnum
MuddyWater
Patchwork
Threat Group-3390

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

Target environment must ingest sysmon data, specifically Event ID 1 with process integrity level data.

Known False Positives

Including Werfault.exe may cause some unintended false positives related to normal application faulting, but is used in a number of UAC bypass techniques.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
A UAC bypass behavior was detected by parent process name- $parent_process_name$ on host $dest$ by $user$. 64 80 80
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 4