Excessive ICMP Unreachables

Rule ID

PH_Rule_Excessive_ICMP_Unreachables

Default Status

Enabled

Description

Detects an usually high frequency of ICMP destination unreachable packets between the same source and destination - this indicates routing error

Severity

MITRE ATT&CK® Tactics

Network

MITRE ATT&CK® Techniques

No Technique Specified

Impacts

Network

Data Source

FortiGate via Syslog or Netflow, Checkpoint via Syslog or Netflow, Palo Alto via Syslog or Netflow

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.

ExcessICMPUnreach

SubPattern Definitions

SubPattern Name: ExcessICMPUnreach

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

ipProto = 1 AND icmpType = 3 AND eventType IN (Group@PH_SYS_EVENT_PermitNetTraffic, Group@PH_SYS_EVENT_NetflowTraffic, Group@PH_SYS_EVENT_BiNetflowTraffic, Group@PH_SYS_EVENT_DenyNetTraffic) AND srcIpAddr NOT IN (Group@PH_SYS_APP_ACCELOPS,Group@PH_SYS_DEVICE_FSM)

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, destIpAddr

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

 srcIpAddr = ExcessICMPUnreach.srcIpAddr,
 destIpAddr =ExcessICMPUnreach.destIpAddr

FortiSIEM Rules