Patent ID: 8464329

Claim:
A security device for SIP-based communication sessions, the security device comprising: a firewall acting between SIP user agents, services and devices on a private network and a public network, the firewall including a blacklist of undesired SIP sources which are prevented from traversing the security device; a Network Address Translator and Port Address Translator to alter the addresses and/or ports of data traversing the security device to hide addresses and ports on the private network from the public network; a hardened SIP stack operable to examine all SIP messages traversing the security device to identify malformed messages and to discard said malformed messages; an admission control process to identify a resource requested for use by an external user agent in a session to be established by a selected SIP message traversing the security device, wherein the requested resource is identified using resource request information in the selected SIP message, and to determine whether to refuse the session before the session is established based on the identified resource and a current resource utilization; and a plurality of security processes to examine pre-selected SIP messages in accordance with one or more rules to prevent malicious attacks on SIP devices and/or services within the private network.