This indicates detection of an attempted brute force login from SIPVicious svcrack.
SIPVicious is a SIP scanner. The signature detects for SIP requests from the scanner at a rate of 100 per second. The rate can be adjusted in the CLI or GUI to suit your needs.
SIP based VoIP systems
System Compromise: Remote attackers can gain access to the service provided by the vulnerable systems.
Monitor the traffic from that network for any suspicious activity.
Adjust the threshold for the signature accordingly.