Windows: Possible Process Hollowing Image Loading

Rule ID

PH_Rule_SIGMA_334

Default Status

Enabled

Description

Detects Loading of samlib.dll, WinSCard.dll from untypical process e.g. through process hollowing by Mimikatz. Mimikatz is a open source malware program that is commonly used by hackers and security professionals to extract sensitive information, such as passwords and credentials, from a system's memory. Process hollowing is a defense evasion technique that runs custom code within the address space of another process, thereby avoiding detection. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_susp_uncommon_image_load.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

T1574.002

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

Mimikatz is intended to be used by penetration testers and security red teams to simulate a real cyberthreat. Investigate whether the user needs to really run Mimikatz. Investigate what other incidents are occurring on that host during that time frame. If necessary, rebuild the host from a known, good source and have the user change their password.

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 "\\notepad\.exe$" AND loadedProcName REGEXP "\\WinSCard\.dll$|\\samlib\.dll$"

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