PH_Rule_SIGMA_2557
Enabled
Detect use of the Windows 8.3 short name. Which could be used as a method to avoid Image detection. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_susp_ntfs_short_name_path_use_image.yml
5
Security
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/TA0005T1564.004
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/T1564/004Server
Windows Sysmon via FortiSIEM Agent
Correlation
No remediation guidance specified
If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.
300 seconds
If the following defined pattern/s occur within a 300 second time window.
Filter
This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.
This is the query logic that matches incoming events
eventType="Win-Sysmon-1-Create-Process" AND procName REGEXP ".*~1\\.*|.*~2\\.*" AND ((parentProcName NOT IN ("C:\\Windows\\System32\\Dism.exe","C:\\Windows\\System32\\cleanmgr.exe") AND parentProcName NOT REGEXP "\\WebEx\\WebexHost\.exe$|\\thor\\thor64\.exe$" AND product!="InstallShield (R)" AND description!="InstallShield (R) Setup Engine" AND company!="InstallShield Software Corporation") AND (procName NOT REGEXP ".*\\AppData\\.*" OR procName NOT REGEXP ".*\\Temp\\.*" AND procName NOT REGEXP "~1\\7zG\.exe$|~1\\unzip\.exe$"))
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
company,description,hostName,parentProcName,procName,product
This is most typically a numerical constraint that defines when the rule should trigger an incident
COUNT(*) >= 1
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
company = Filter.company,
description = Filter.description,
hostName = Filter.hostName,
parentProcName = Filter.parentProcName,
procName = Filter.procName,
product = Filter.product