PH_Rule_SIGMA_836
Enabled
Detects the creation of a new Outlook form which can contain malicious code. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_office_outlook_newform.yml
7
Security
Persistence
Persistence consists of techniques that adversaries use to keep access to systems across restarts, changed credentials, and other interruptions that could cut off their access. Techniques used for persistence include any access, action, or configuration changes that let them maintain their foothold on systems, such as replacing or hijacking legitimate code or adding startup code.
https://attack.mitre.org/tactics/TA0003T1137.003
Office Application Startup: Outlook Forms
Adversaries may abuse Microsoft Outlook forms to obtain persistence on a compromised system. Outlook forms are used as templates for presentation and functionality in Outlook messages. Custom Outlook forms can be created that will execute code when a specifically crafted email is sent by an adversary utilizing the same custom Outlook form. Once malicious forms have been added to the user's mailbox, they will be loaded when Outlook is started. Malicious forms will execute when an adversary sends a specifically crafted email to the user.
https://attack.mitre.org/techniques/T1137/003Server
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-11-FileCreate" AND procName REGEXP "\\outlook\.exe$" AND fileName REGEXP ".*\\AppData\\Local\\Microsoft\\FORMS\\IPM.*|.*\\Local Settings\\Application Data\\Microsoft\\Forms.*"
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
fileName,hostName,procName
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
fileName = Filter.fileName,
hostName = Filter.hostName,
procName = Filter.procName