SAM Database File Access Attempt

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Description

The following analytic identifies access to SAM, SYSTEM or SECURITY databases' within the file path of windows\system32\config using Windows Security EventCode 4663. This particular behavior is related to credential access, an attempt to either use a Shadow Copy or recent CVE-2021-36934 to access the SAM database. The Security Account Manager (SAM) is a database file in Windows XP, Windows Vista, Windows 7, 8.1 and 10 that stores users' passwords.

• Type: Hunting

• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

• Last Updated: 2021-07-23
• Author: Michael Haag, Mauricio Velazco, Splunk
• ID: 57551656-ebdb-11eb-afdf-acde48001122

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1003.002	Security Account Manager	Credential Access

T1003

OS Credential Dumping

Credential Access

Kill Chain Phase

• Exploitation

NIST

• DE.AE

CIS20

• CIS 10

CVE

ID	Summary	CVSS
CVE-2021-36934	Windows Elevation of Privilege Vulnerability	4.6

Search

`wineventlog_security` (EventCode=4663)  process_name!=*\\dllhost.exe Object_Name IN ("*\\Windows\\System32\\config\\SAM*","*\\Windows\\System32\\config\\SYSTEM*","*\\Windows\\System32\\config\\SECURITY*") 
| stats values(Accesses) count by process_name Object_Name  dest user 
| `sam_database_file_access_attempt_filter`

Macros

The SPL above uses the following Macros:

• wineventlog_security

sam_database_file_access_attempt_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

• _time
• process_name
• Object_Name
• dest
• user

How To Implement

To successfully implement this search, you must ingest Windows Security Event logs and track event code 4663. For 4663, enable "Audit Object Access" in Group Policy. Then check the two boxes listed for both "Success" and "Failure."

Known False Positives

Natively, dllhost.exe will access the files. Every environment will have additional native processes that do as well. Filter by process_name. As an aside, one can remove process_name entirely and add Object_Name=*ShadowCopy*.

Associated Analytic Story

• Credential Dumping

RBA

Risk Score	Impact	Confidence	Message
80.0	80	100	The following process $process_name$ accessed the object $Object_Name$ attempting to gain access to credentials on $dest$ by user $user$.

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

• https://www.ultimatewindowssecurity.com/securitylog/encyclopedia/event.aspx?eventID=4663
• https://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4663
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36934
• https://github.com/GossiTheDog/HiveNightmare
• https://github.com/JumpsecLabs/Guidance-Advice/tree/main/SAM_Permissions
• https://en.wikipedia.org/wiki/Security_Account_Manager

Test Dataset

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

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