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Refused Sessions

The Refused Sessions sensor looks for a pattern in refused sessions. Refused session counts may indicate a SYN attack or a server that cannot respond to all requests.

Troubleshooting a Refused Sessions Alert

A server tends to stop fulfilling and refusing sessions when it reaches its capacity to handle more data. Sessions also may be refused because a load balancer is sending heart beat messages to the servers.

Refused Sessions counts also may result when legitimate traffic overloads a server that has inadequate resources for additional TCP session requests.

An alert may indicate a SYN or RST flood. If this is the case, the anomaly should be visible in the Enterprise-Wide Correlated Anomalies view.