Next-generation firewalls will need wide variety of features

It may be time to upgrade to devices with a wider variety of defenses

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.

Proxying SSL is an approach being taken by Blue Coat and Palo Alto Networks, among others. Palo Alto says its gear can be configured to permit some SSL traffic without proxying, such as personal online banking as determined by packet headers.

The gear also distinguishes among different flavors of similar traffic such as e-mail, and can impose fine-grained rules. For instance it could allow both Yahoo Mail and Outlook mail, but blocking attachments from Yahoo Mail.

SanDisk is trialing Palo Alto gear in monitoring mode, and finds the visibility it gives in to application use on the network to be valuable, says Justin Smith, the company's network architect. When the product is installed inline in a few weeks, he says it will also enforce rules based on users, not just machines. So if a user logs in from a different switch port or VLAN, the firewall will enforce the same user-based rules, Smith says.

He says the device recognizes applications themselves, not just what port they use so if an unauthorized application switches ports, the gear can still block it.

Another alternative is to consider moving the location of deep-inspection firewall protection, Whitelely says. Personal firewalls can be installed on desktops and laptops, and application layer gateways can filter traffic as it approaches critical network assets.

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Tim Greene

Network World

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