PH_Rule_SIGMA_578
Enabled
Detects suspicious encoded character syntax often used for defense evasion. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_obfuscation_via_utf8.yml
7
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/TA0005T1027.003
Obfuscated Files or Information: Steganography
Adversaries may use steganography techniques in order to prevent the detection of hidden information. Steganographic techniques can be used to hide data in digital media such as images, audio tracks, video clips, or text files.
https://attack.mitre.org/techniques/T1027/003T1132.001
Data Encoding: Standard Encoding
Adversaries may encode data with a standard data encoding system to make the content of command and control traffic more difficult to detect. Common data encoding schemes include ASCII, Unicode, hexadecimal, Base64, and MIME. Some data encoding systems may also result in data compression, such as gzip.
https://attack.mitre.org/techniques/T1132/001Server
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 command REGEXP ".*\(WCHAR\)0x.*"
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
command,hostName
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
command = Filter.command,
hostName = Filter.hostName