The Jericho Forum predicts a day when it will be unnecessary to build network perimeter defenses with firewalls, but in the meantime corporate network-security experts need to find alternatives to address the shortcomings that are pushing firewalls toward extinction.

They need to look for equipment that filters at the application layer and supplemental products that proxy encrypted traffic so it can be inspected, experts say.

“A next-generation firewall needs to look within traffic streams and determine whether this is the traffic I expected,” says Rob Whiteley, an analyst with Forrester Research. The key to protection is peering deep into packets to decide what poses a threat and what doesn’t, not merely on what ports it uses, he says.

Firewall vendors already recognize this and have incorporated deep inspection of packets that probe to the application layer to determine the nature of traffic and look for anomalies that can signal malicious behavior, he says.

Most businesses leave open port 80 for HTTP and port 443 for SSL, and these protocols are used to transport a wide variety of traffic and applications, legitimate and otherwise, says Greg Young, an analyst with Gartner. With these ports unguarded, traditional firewalls allow in more potentially damaging traffic. Implementing Web-based networking accelerates the problem.

SSL traffic, which is growing rapidly as a percentage of corporate traffic, poses a particular problem because there is no way for a firewall to decrypt it to find out what it contains, Young says. “The fact is this is a real blind spot. It’s a dirty little secret that a large percentage of traffic is not being inspected,” he says.

The only way around the problem is to terminate the SSL, decrypt it and inspect it, which effectively creates a man-in-the-middle attack, albeit an authorized one, he says. Nevertheless, it still breaks the security model that encryption secures traffic end-to-end as a way to thwart man-in-the-middle attacks, says Young.

Businesses have to weigh the chances of damage from traffic that comes in encrypted vs. damage that could come about by breaking terminating the SSL session before its destination. “The odds of bad things coming through the SSL sessions are higher,” he says.