Windows: Use NTFS Short Name in Image

Rule ID

PH_Rule_SIGMA_2559

Default Status

Enabled

Description

Detect use of the Windows 8.3 short name. Which could be used as a method to avoid Image based detection. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_susp_ntfs_short_name_use_image.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

T1564.004

Hide Artifacts: NTFS File Attributes

Adversaries may use New Technology File System (NTFS) file attributes to hide their malicious data in order to evade detection. Every NTFS formatted partition contains a Master File Table (MFT) that maintains a record for every file/directory on the partition. Within MFT entries are file attributes, such as Extended Attributes (EA) and Data, that can be used to store arbitrary data (and even complete files). Adversaries may store malicious data or binaries in file attribute metadata instead of directly in files. This may be done to evade some defenses, such as static indicator scanning tools and anti-virus.

https://attack.mitre.org/techniques/T1564/004

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 ".*~1\.bat.*|.*~1\.dll.*|.*~1\.exe.*|.*~1\.hta.*|.*~1\.js.*|.*~1\.msi.*|.*~1\.ps1.*|.*~1\.vbe.*|.*~1\.vbs.*|.*~2\.bat.*|.*~2\.dll.*|.*~2\.exe.*|.*~2\.hta.*|.*~2\.js.*|.*~2\.msi.*|.*~2\.ps1.*|.*~2\.vbe.*|.*~2\.vbs.*" AND (parentProcName NOT REGEXP "-installer\.exe$|\\WebEx\\WebexHost\.exe$|\\thor\\thor64\.exe$" AND procName NOT REGEXP ".*\\vcredi.*" AND parentProcName!="C:\\Windows\\explorer.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

hostName,parentProcName,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,
parentProcName = Filter.parentProcName,
procName = Filter.procName

FortiSIEM Rules