Sudden Increase in Failed Logons To A Host

Rule ID

PH_Rule_Stat_24

Default Status

Enabled

Description

Detects a sudden 50% increase of failed logons to a specific host over a 30 minute window

Severity

MITRE ATT&CK® Tactics

Initial Access

Initial Access consists of techniques that use various entry vectors to gain their initial foothold within a network. Techniques used to gain a foothold include targeted spearphishing and exploiting weaknesses on public-facing web servers. Footholds gained through initial access may allow for continued access, like valid accounts and use of external remote services, or may be limited-use due to changing passwords.

https://attack.mitre.org/tactics/TA0001

MITRE ATT&CK® Techniques

T1078.003

Valid Accounts: Local Accounts

Adversaries may obtain and abuse credentials of a local account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Local accounts are those configured by an organization for use by users, remote support, services, or for administration on a single system or service. Local Accounts may also be abused to elevate privileges and harvest credentials through [OS Credential Dumping.

https://attack.mitre.org/techniques/T1078/003

Impacts

Server

Data Source

Detection

Profiling

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.

1800 seconds

Trigger Conditions

If the following defined pattern/s occur within a 1800 second time window.

Logon

SubPattern Definitions

SubPattern Name: Logon

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_HostLogonFailure)

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

reptDevName,reptDevIpAddr

Aggregate Constraint

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

COUNT(*) >= 10 AND
	  COUNT(*) >= 1.50 * STAT_AVG(COUNT(*):122)

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 = Logon.reptDevName,
 hostIpAddr = Logon.reptDevIpAddr,
 count = Logon.COUNT(*),
 avgMatchedEvents = Logon.STAT_AVG(COUNT(*):122)

FortiSIEM Rules