Repeated Multiple Logon Failures: VPN

Rule ID

PH_Rule_Access_26

Default Status

Disabled

Description

Detects repeating occurrences of excessive VPN logon failures

Severity

MITRE ATT&CK® Tactics

Credential Access

Credential Access consists of techniques for stealing credentials like account names and passwords. Techniques used to get credentials include keylogging or credential dumping. Using legitimate credentials can give adversaries access to systems, make them harder to detect, and provide the opportunity to create more accounts to help achieve their goals.

https://attack.mitre.org/tactics/TA0006

MITRE ATT&CK® Techniques

T1110.001

Brute Force: Password Guessing

Adversaries with no prior knowledge of legitimate credentials within the system or environment may guess passwords to attempt access to accounts.

https://attack.mitre.org/techniques/T1110/001

Impacts

Network

Data Source

FortiGate via Syslog, FortiProxy via Syslog, Juniper JunOS via Syslog, Juniper SRX Via Syslog, Juniper SSG via Syslog, Pulse Secure via Syslog, Hillstone Firewall Via Syslog, Cisco ASA via Syslog, Cisco IOS Via Syslog, WatchGuard via Syslog, Sophos Firewall via Syslog, SonicOS via Syslog

Detection

Correlation

Remediation Guidance

Identify the source of the incident and the user and make sure that it is a legitimate attempt to log on to the system. Make sure it is not a cached credential from another system while the primary user has changed credential. Make sure there are no other incidents from the source host that may indicate malware trying to gain access to other systems. Make sure there are no vulnerabilities on the source and destination hosts.

Time Window

If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.

86400 seconds

Trigger Conditions

If the following defined pattern/s occur within a 86400 second time window.

RepeatExcessVPNLoginFailure

SubPattern Definitions

SubPattern Name: RepeatExcessVPNLoginFailure

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 = "PH_RULE_EXCESS_FAILED_LOGON_VPN"

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

srcIpAddr,destName, destIpAddr

Aggregate Constraint

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

COUNT (*) >= 3

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

 srcIpAddr = RepeatExcessVPNLoginFailure.srcIpAddr,
 destName = RepeatExcessVPNLoginFailure.destName,
 destIpAddr = RepeatExcessVPNLoginFailure.destIpAddr,
 incidentCount = RepeatExcessVPNLoginFailure.COUNT(*)

FortiSIEM Rules