Detection: Wbemprox COM Object Execution

Updated Date: 2024-05-13 ID: 9d911ce0-c3be-11eb-b177-acde48001122 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects a suspicious process loading a COM object from wbemprox.dll, fastprox.dll, or wbemcomn.dll. It leverages Sysmon EventCode 7 to identify instances where these DLLs are loaded by processes not typically associated with them, excluding known legitimate processes and directories. This activity is significant as it may indicate an attempt by threat actors to abuse COM objects for privilege escalation or evasion of detection mechanisms. If confirmed malicious, this could allow attackers to gain elevated privileges or maintain persistence within the environment, posing a significant security risk.

Search

1`sysmon` EventCode=7  ImageLoaded IN ("*\\fastprox.dll", "*\\wbemprox.dll", "*\\wbemcomn.dll") NOT (process_name IN ("wmiprvse.exe", "WmiApSrv.exe", "unsecapp.exe")) NOT(Image IN("*\\windows\\*","*\\program files*", "*\\wbem\\*")) 
2| stats count min(_time) as firstTime max(_time) as lastTime by Image ImageLoaded process_name dest EventCode Signed ProcessId Hashes IMPHASH 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `wbemprox_com_object_execution_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Sysmon EventID 7	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
wbemprox_com_object_execution_filter	`search *`

wbemprox_com_object_execution_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
T1218	System Binary Proxy Execution	Defense Evasion
T1218.003	CMSTP	Defense Evasion

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

Lazarus Group

Cobalt Group

MuddyWater

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

To successfully implement this search, you need to be ingesting logs with the process name and imageloaded executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

legitimate process that are not in the exception list may trigger this event.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Suspicious COM Object Execution on $dest$	35	70	50

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: 2