Detection: Windows KrbRelayUp Service Creation

Updated Date: 2024-05-09 ID: e40ef542-8241-4419-9af4-6324582ea60a Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the creation of a service with the default name "KrbSCM" associated with the KrbRelayUp tool. It leverages Windows System Event Logs, specifically EventCode 7045, to identify this activity. This behavior is significant as KrbRelayUp is a known tool used for privilege escalation attacks. If confirmed malicious, this activity could allow an attacker to escalate privileges, potentially gaining unauthorized access to sensitive systems and data.

Search

1`wineventlog_system` EventCode=7045 ServiceName IN ("KrbSCM") 
2| stats count min(_time) as firstTime max(_time) as lastTime by dest EventCode ImagePath ServiceName StartType ServiceType 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `windows_krbrelayup_service_creation_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Windows Event Log System 7045	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:System'`	N/A

Macros Used

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

windows_krbrelayup_service_creation_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
T1543.003	Windows Service	Persistence

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

APT19

APT3

APT32

APT38

APT41

Blue Mockingbird

Carbanak

Cinnamon Tempest

Cobalt Group

DarkVishnya

Earth Lusca

FIN7

Ke3chang

Kimsuky

Lazarus Group

PROMETHIUM

TeamTNT

Threat Group-3390

Tropic Trooper

Wizard Spider

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 Windows System Event Logs with 7045 EventCode enabled. The Windows TA is also required.

Known False Positives

False positives should be limited as this is specific to KrbRelayUp based attack. Filter as needed.

Associated Analytic Story

Local Privilege Escalation With KrbRelayUp

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A service was created on $dest$, related to KrbRelayUp.	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

https://github.com/Dec0ne/KrbRelayUp

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:System`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:System`	`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: 3