Windows: Deny Service Access Using Security Descriptor Tampering Via Sc.EXE

Rule ID

PH_Rule_SIGMA_2517

Default Status

Enabled

Description

Detects suspicious DACL modifications to deny access to a service that affects critical trustees. This can be used to hide services or make them unstoppable. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_sc_sdset_deny_service_access.yml

Severity

MITRE ATT&CK® Tactics

Persistence

Persistence consists of techniques that adversaries use to keep access to systems across restarts, changed credentials, and other interruptions that could cut off their access. Techniques used for persistence include any access, action, or configuration changes that let them maintain their foothold on systems, such as replacing or hijacking legitimate code or adding startup code.

https://attack.mitre.org/tactics/TA0003

MITRE ATT&CK® Techniques

T1543.003

Create or Modify System Process: Windows Service

Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions. Adversaries may install a new service or modify an existing service by using system utilities to interact with services, by directly modifying the Registry, or by using custom tools to interact with the Windows API. Adversaries may configure services to execute at startup in order to persist on a system. An adversary may also incorporate Masquerading by using a service name from a related operating system or benign software, or by modifying existing services to make detection analysis more challenging. Modifying existing services may interrupt their functionality or may enable services that are disabled or otherwise not commonly used. Services may be created with administrator privileges but are executed under SYSTEM privileges, so an adversary may also use a service to escalate privileges from administrator to SYSTEM.

https://attack.mitre.org/techniques/T1543/003

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-1-Create-Process" AND (procName REGEXP "\\sc\.exe$" OR srcFileName="sc.exe") AND (command REGEXP ".*sdset.*" AND command REGEXP ".*D;.*") AND command REGEXP ".*;BA.*|.*;IU.*|.*;SU.*|.*;SY.*|.*;WD.*"

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

command,hostName,procName,srcFileName

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

command = Filter.command,
hostName = Filter.hostName,
procName = Filter.procName,
srcFileName = Filter.srcFileName

FortiSIEM Rules