VoIP is a future of telecom and some of the telcos are started using OpenSources VoIP solution in his network. Kamailio and Freeswitch are good to use for scalable and high volume solutions.Kamailio is good to use as a SIP proxy in the VoIP network. Kamailio provides multiple modules from that list “exec” module is providing the option to execute the shell commands.
IPTABLES is one of network security tool which is filtering the traffic. OV500 is using the “exec” Kamailio module for blocking the unauthorized traffic source and restricting the unwanted traffic.