FortiSIEM Rules

Transient Windows Account Usage

Rule ID

PH_Rule_Access_67

Default Status

Enabled

Description

Detects that an account was created, used and then deleted within a short period of time. This is highly unusual activity and must be thoroughly investigated.

Severity

9

Category

Security

MITRE ATT&CK® Tactics

Suspicious Activity

MITRE ATT&CK® Techniques

No Technique Specified

Impacts

Server

Data Source

Windows Security Log via OMI or 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.

3600 seconds

Trigger Conditions

If the following defined pattern/s occur within a 3600 second time window.

AccountCreated FOLLOWED_BY LogonSuccess FOLLOWED_BY AccountDeleted

Global Constraint

This defines how two or more distinct events are related in a time-series based action. e.g. An event occurs followed by another event if the source IP, user, and messageId are the same

AccountCreated.targetUser = LogonSuccess.user AND LogonSuccess.user = AccountDeleted.targetUser AND LogonSuccess.reptDevName = AccountDeleted.reptDevName

SubPattern Definitions

SubPattern Name: AccountCreated

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 IN (Group@PH_SYS_EVENT_AccountCreated)

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

user,targetUser,reptDevName

Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 1
Operator Rank: 0 Operator Type: FOLLOWED_BY

This operator defines the logic condition relating to the prior event subpattern clause and the following event subpattern clause

SubPattern Name: LogonSuccess

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 IN (Group@PH_SYS_EVENT_HostLogonSuccess,Group@PH_SYS_EVENT_DomainLogonSuccess)

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

user,reptDevName

Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 1
Operator Rank: 1 Operator Type: FOLLOWED_BY

This operator defines the logic condition relating to the prior event subpattern clause and the following event subpattern clause

SubPattern Name: AccountDeleted

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 IN (Group@PH_SYS_EVENT_AccountDeleted)

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

targetUser,reptDevName

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

 user = AccountCreated.user,
 targetUser = AccountCreated.targetUser,
 destName = AccountCreated.reptDevName