FortiSIEM Rules

Degraded VoIP Call Quality

Rule ID


Default Status



Detects degraded VoIP call quality (mos score between 2.2 and 3.5) from CDR records. Calls originating from VPN Pools are excluded.







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.

MITRE ATT&CK® Techniques


Endpoint Denial of Service: Service Exhaustion Flood

Adversaries may target the different network services provided by systems to conduct a DoS. Adversaries often target DNS and web services, however others have been targeted as well. One example of this type of attack is known as a simple HTTP flood, where an adversary sends a large number of HTTP requests to a web server to overwhelm it and/or an application that runs on top of it. Another variation, known as a SSL renegotiation attack, the adversary establishes a SSL/TLS connection and then proceeds to make a series of renegotiation requests. Because the cryptographic renegotiation has a meaningful cost in computation cycles, this can cause an impact to the availability of the service when done in volume.



Data Source

Cisco Call Manager via CDR Records



Remediation Guidance

This is likely a network connectivity issue or VoIP component server performance issye.

Time Window

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

900 seconds

Trigger Conditions

If the following defined pattern/s occur within a 900 second time window.


SubPattern Definitions

SubPattern Name: DegradedCallQuality

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 = "Cisco-CM-CDR" AND mosScore > 2.2 AND mosScore <= 3.5 AND srcIpAddr NOT IN (Group@PH_SYS_VPN_ADDRESS_POOL)

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


Aggregate Constraint

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

COUNT (*) >= 2 AND AVG(mosScore) > 2.2 AND AVG(mosScore) <= 3.5

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 = DegradedCallQuality.srcIpAddr,
 mosScore = DegradedCallQuality.AVG(mosScore)