Windows: InstallerFileTakeOver LPE CVE-2021-41379 File Create Event

Rule ID

PH_Rule_SIGMA_890

Default Status

Enabled

Description

Detects signs of the exploitation of LPE CVE-2021-41379 that include an msiexec process that creates an elevation_service.exe file. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_cve_2021_41379_msi_lpe.yml

Severity

MITRE ATT&CK® Tactics

Privilege Escalation

Privilege Escalation consists of techniques that adversaries use to gain higher-level permissions on a system or network. Adversaries can often enter and explore a network with unprivileged access but require elevated permissions to follow through on their objectives. Common approaches are to take advantage of system weaknesses, misconfigurations, and vulnerabilities.

https://attack.mitre.org/tactics/TA0004

MITRE ATT&CK® Techniques

T1068

Exploitation for Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to collect elevate privileges. An adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code. They will likely need to perform privilege escalation to include use of software exploitation to circumvent those restrictions.

https://attack.mitre.org/techniques/T1068

Impacts

Server

Data Source

Windows Sysmon via FortiSIEM Agent

Detection

Correlation

Remediation Guidance

No remediation guidance specified

Time Window

If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.

300 seconds

Trigger Conditions

If the following defined pattern/s occur within a 300 second time window.

Filter

SubPattern Definitions

SubPattern Name: Filter

This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.

SubPattern Query

This is the query logic that matches incoming events

eventType="Win-Sysmon-11-FileCreate" AND procName REGEXP "\\msiexec\.exe$" AND fileName REGEXP "^C:\\Program Files \(x86\)\\Microsoft\\Edge\\Application" AND fileName REGEXP "\\elevation_service\.exe$"

Group by Attributes

This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID

fileName,hostName,procName

Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 1

Incident Attribute Mapping

This section defines which fields in matching raw events should be mapped to the incident attributes in the resulting incident.

The available raw event attributes to map are limited to the group by attributes and the aggregate event constraint fields for each subpattern

fileName = Filter.fileName,
hostName = Filter.hostName,
procName = Filter.procName

FortiSIEM Rules