May 23 2008   12:20AM GMT

It’s Not Your Mother’s Firewall Anymore – Part I

Arian Eigen Heald Arian Eigen Heald Profile: Arian Eigen Heald

In the northern part of Maine, (north of Portland, where I live) folks go about their business without locking their doors or even leaving their cars running while they go into the store. (When it’s -10 degrees, it’s good to have the car run a little more). This describes the fundamental trust the people there have in their community and their neighbors. If you drive by a sign on a driveway that advertises fruits or vegetables for sale, often there will be no person there to collect the money, just a basket with a “thank you” tag. During the winter, folks on the highway will pull over and run down the bank to help a car that has just slid off the road.

The bigger businesses do lock their doors, because they don’t know everyone who might come into their store, and don’t trust unknown people to care or pay for their merchandise.

Fifteen years ago, many businesses did not have a firewall between them and the Internet. You couldn’t pay for something online, or do business-to-business operations. The value of the information was lower, and there was a higher level of trust.

The other issue that came along was the limitation of IP4 addressing. NAT (Network Address Translation) allowed networks of any size to use non-internet routeable subnets as long as they were behind a firewall that had an outside (Internet-facing) legal IP address. (It’s why you don’t see addresses on the Internet for the 10.x.x.x, 172.16.x.x and 192.168.1.x).

Turns out that NAT and firewalls made perfect friends; behind a NAT enabled firewall, a huge network could exist and have all private IPs that the Internet cannot route to or see. The firewall acts as a gatekeeper and monitor, with an internal NIC (Network Interface card) that has an internal private address and an external NIC for Internet communications.

Today, I can ping a server in Russia on my desktop, and that server in Russia could ping me back, if I were not behind a firewall. My Northern neighbors, many of whom have a computer at home, can also ping that far away server. Our “neighbors” on the Internet are people we do not know, and many of them have the ability to “break in” without ever having to knock on our doors or even try the lock. There is zero trust on the Internet.

What does this have to do with IT Auditing, for heaven’s sake? Well, I see too many firewall configurations set up without any safeguards against the bad Internet neighbors. And I see too many auditors who say, “Oh, you have a firewall, that’s good.” They never ask to see the configuration and examine it carefully. (Security by checklist) Management seem to think that just having one is enough. They don’t send their folks to be trained on how to use it, or they outsource the management of their firewall and never inspect the rules or the logs.

Eigen’s Security Rules of Thumb #2: You can outsource function, but you cannot outsource responsibility.

I’ve seen outsourced firewalls that allowed every single IP address of the vendor access into the firewalled company’s network. It was easier for them to get to other network devices they managed, but there were no access controls as to who on their network could come in, or any logging, either. No one from the company looked at the configuration until I came along and said, “Why do they need that?”

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