Excessive HTTP Client Side Errors

Rule ID

PH_Rule_Web_Server_1

Default Status

Enabled

Description

Detects multiple HTTP client side errors from the same IP - might indicate an attack . Thresholds are 5 errors from the same src IP within a 10 minute interval

Severity

MITRE ATT&CK® Tactics

Impact

Impact consists of techniques that adversaries use to disrupt availability or compromise integrity by manipulating business and operational processes. Techniques used for impact can include destroying or tampering with data. In some cases, business processes can look fine, but may have been altered to benefit the adversaries’ goals. These techniques might be used by adversaries to follow through on their end goal or to provide cover for a confidentiality breach.

https://attack.mitre.org/tactics/TA0040

MITRE ATT&CK® Techniques

T1498.001

Network Denial of Service: Direct Network Flood

Adversaries may attempt to cause a denial of service (DoS) by directly sending a high-volume of network traffic to a target. Almost any network protocol may be used for flooding. Stateless protocols such as UDP or ICMP are commonly used but stateful protocols such as TCP can be used as well. Botnets are commonly used to conduct network flooding attacks against networks and services. Large botnets can generate a significant amount of traffic from systems spread across the global Internet. In some of the worst cases for distributed DoS (DDoS), so many systems are used to generate the flood that each one only needs to send out a small amount of traffic to produce enough volume to saturate the target network. In such circumstances, distinguishing DDoS traffic from legitimate clients becomes exceedingly difficult.

https://attack.mitre.org/techniques/T1498/001

Impacts

Application

Data Source

Microsoft IIS via FortiSIEM Agent, Apache via Syslog, Squid log via Syslog

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.

600 seconds

Trigger Conditions

If the following defined pattern/s occur within a 600 second time window.

ExcessHTTPClientErr

SubPattern Definitions

SubPattern Name: ExcessHTTPClientErr

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 ("IIS-Web-Forbidden-Access-Denied","IIS-Web-Bad-Request","IIS-Web-Length-Reqd-Access-Denied","Apache-Web-Forbidden-Access-Denied","Apache-Web-Bad-Request","Apache-Web-Length-Reqd-Access-Denied","Squid-Web-Forbidden-Access-Denied","Squid-Web-Bad-Request","Squid-Web-Length-Reqd-Access-Denied")

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,reptDevIpAddr,reptDevName

Aggregate Constraint

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

COUNT (*) >= 5

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 = ExcessHTTPClientErr.srcIpAddr,
 destIpAddr = ExcessHTTPClientErr.reptDevIpAddr,
destName = ExcessHTTPClientErr.reptDevName,
 incidentCount = ExcessHTTPClientErr.COUNT(*)

FortiSIEM Rules