Detection: PetitPotam Network Share Access Request

Updated Date: 2024-05-26 ID: 95b8061a-0a67-11ec-85ec-acde48001122 Author: Michael Haag, Mauricio Velazco, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects network share access requests indicative of the PetitPotam attack (CVE-2021-36942). It leverages Windows Event Code 5145, which logs attempts to access network share objects. This detection is significant as PetitPotam can coerce authentication from domain controllers, potentially leading to unauthorized access. If confirmed malicious, this activity could allow attackers to escalate privileges or move laterally within the network, posing a severe security risk. Ensure Event Code 5145 is enabled via Group Policy to utilize this analytic effectively.

Search

1`wineventlog_security` SubjectUserName="ANONYMOUS LOGON" EventCode=5145 RelativeTargetName=lsarpc 
2| stats count min(_time) as firstTime max(_time) as lastTime by dest, SubjectUserSid, ShareName, src, AccessMask, AccessReason 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `petitpotam_network_share_access_request_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Windows Event Log Security 5145	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Security'`	N/A

Macros Used

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

petitpotam_network_share_access_request_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
T1187	Forced Authentication	Credential Access

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

DarkHydrus

Dragonfly

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

Windows Event Code 5145 is required to utilize this analytic and it may not be enabled in most environments.

Known False Positives

False positives have been limited when the Anonymous Logon is used for Account Name.

Associated Analytic Story

PetitPotam NTLM Relay on Active Directory Certificate Services

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A remote host is enumerating a $dest$ to identify permissions. This is a precursor event to CVE-2021-36942, PetitPotam.	56	80	70

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:Security`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Security`	`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