Windows: Svchost DLL Search Order Hijack

Rule ID

PH_Rule_SIGMA_343

Default Status

Enabled

Description

Detects DLL sideloading of DLLs that are loaded by the SCM for some services (IKE, IKEEXT, SessionEnv) which do not exists on a typical modern system IKEEXT and SessionEnv service, as they call LoadLibrary on files that do not exist within C:\Windows\System32\ by default. An attacker can place their malicious logic within the PROCESS_ATTACH block of their library and restart the aforementioned services "svchost.exe -k netsvcs" to gain code execution on a remote machine. . This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_side_load_svchost_dlls.yml

Severity

MITRE ATT&CK® Tactics

Defense Evasion

Defense Evasion consists of techniques that adversaries use to avoid detection throughout their compromise. Techniques used for defense evasion include uninstalling/disabling security software or obfuscating/encrypting data and scripts. Adversaries also leverage and abuse trusted processes to hide and masquerade their malware. Other tactics’ techniques are cross-listed here when those techniques include the added benefit of subverting defenses.

https://attack.mitre.org/tactics/TA0005

MITRE ATT&CK® Techniques

T1574.001

Hijack Execution Flow: DLL Search Order Hijacking

Adversaries may execute their own malicious payloads by hijacking the search order used to load DLLs. Windows systems use a common method to look for required DLLs to load into a program. Hijacking DLL loads may be for the purpose of establishing persistence as well as elevating privileges and/or evading restrictions on file execution. If a search order-vulnerable program is configured to run at a higher privilege level, then the adversary-controlled DLL that is loaded will also be executed at the higher level. In this case, the technique could be used for privilege escalation from user to administrator or SYSTEM or from administrator to SYSTEM, depending on the program.

https://attack.mitre.org/techniques/T1574/001

T1574.002

Hijack Execution Flow: DLL Side-Loading

Adversaries may execute their own malicious payloads by hijacking the library manifest used to load DLLs. Adversaries may take advantage of vague references in the library manifest of a program by replacing a legitimate library with a malicious one, causing the operating system to load their malicious library when it is called for by the victim program. Adversaries likely use this technique as a means of masking actions they perform under a legitimate, trusted system or software process.

https://attack.mitre.org/techniques/T1574/002

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-7-Image-Loaded" AND (procName REGEXP "\\svchost\.exe$" AND loadedProcName REGEXP "\\tsmsisrv\.dll$|\\tsvipsrv\.dll$|\\wlbsctrl\.dll$") AND (loadedProcName NOT REGEXP "^C:\\Windows\\WinSxS\\")

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

hostName,loadedProcName,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

 hostName = Filter.hostName,
loadedProcName = Filter.loadedProcName,
procName = Filter.procName

FortiSIEM Rules