Excessive Web Request Failures

Rule ID

PH_RULE_ExcessiveWebRequestFailures

Default Status

Enabled

Description

Calls to one or more web server URIs has returned a status code other than 200 greater than 10 times in a 5 minute interval.

Severity

MITRE ATT&CK® Tactics

Application

MITRE ATT&CK® Techniques

No Technique Specified

Impacts

Application

Data Source

Apache via Syslog, nginx via Syslog, Miocrosoft IIS via FortiSIEM Agent

Detection

Correlation

Remediation Guidance

Identify the root cause and solve the issue

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.

excessive_error_codes

SubPattern Definitions

SubPattern Name: excessive_error_codes

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 CONTAIN "Nginx-"  OR  eventType CONTAIN "Apache-" ) AND httpStatusCode NOT IN ("200","201","202","204")

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,httpStatusCode,srcIpAddr

Aggregate Constraint

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

COUNT(*) >= 10

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

 incidentRptDevName=excessive_error_codes.reptDevName,
httpStatusCode=excessive_error_codes.httpStatusCode,
srcIpAddr=excessive_error_codes.srcIpAddr,
incidentCount=excessive_error_codes.COUNT(*)

FortiSIEM Rules