Windows: Suspicious Windows ANONYMOUS LOGON Local Account Created

Rule ID

PH_Rule_SIGMA_80

Default Status

Enabled

Description

Detects the creation of suspicious accounts similar to ANONYMOUS LOGON, such as using additional spaces. Created as an covering detection for exclusion of Logon Type 3 from ANONYMOUS LOGON accounts. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/builtin/security/win_security_susp_local_anon_logon_created.yml

Severity

MITRE ATT&CK® Tactics

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/TA0003

MITRE ATT&CK® Techniques

T1136.002

Create Account: Domain Account

Adversaries may create a domain account to maintain access to victim systems. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover user, administrator, and service accounts. With a sufficient level of access, the ?net user /add /domain? command can be used to create a domain account. Such accounts may be used to establish secondary credentialed access that do not require persistent remote access tools to be deployed on the system.

https://attack.mitre.org/techniques/T1136/002

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.

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-Security-4720" AND oldTargetUser REGEXP ".*ANONYMOUS.*" AND oldTargetUser REGEXP ".*LOGON.*"

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,oldTargetUser

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,
oldTargetUser = Filter.oldTargetUser

FortiSIEM Rules