Security Corner

Feb 16 2008   8:02PM GMT

How Not to Invite Attackers into Your PCs or Network – the First Line of Defense

Ken Harthun Ken Harthun Profile: Ken Harthun


The other day, I gave you what I consider to be the most basic security maxim, one on which I base all of my security practices: The best security measures are completely useless if you invite attackers into your PCs or networks.

Windows users will remember back before Windows XP Service Pack 2 was released that simply plugging your computer into your cable or DSL modem was almost certain to result in your being compromised in short order. (Who can forget the havoc that Sasser and other worms wreaked before Microsoft wised up and finally turned the firewall on by default?) Running naked with all ports open to the world is a gold-gilt invitation to every criminal and mischief maker on the Internet, and while running a software firewall is a good idea, it’s not nearly enough–crackers already know how to take down XP’s firewall.

Consider this: every IP address owned and/or issued by your Internet Service Provider, no matter who that may be, is constantly being targeted by hackers that are scanning the’Net or worms that are infecting the ‘Net. The IP address assigned to me by my cable Internet provider has been scanned or probed 46 times in the last hour; this goes on 24 hours a day, seven days a week. I certainly don’t want my PC’s software firewall subjected to this kind of thing; yet, most people, not knowing any better, plug their computer directly into the broadband modem. Why do this when there is an inexpensive, simple, yet effective first line of defense available at any big box electronics or office supply superstore–a router?

Through the beauty of Network Address Translation (NAT), even the cheapest router becomes an effective hardware firewall, virtually making your PC invisible to the ‘Net. NAT Router Security Solutions by Steve Gibson of “Security Now!” explains NAT in detail. Here’s one of his illustrations from that article:

A NAT router installed

I must mention that except for one, simple configuration change that is absolutely essential, these simple devices work fine right out of the box. The average user can plug it in and not have to worry about a complicated setup process.

So, here’s Security Maxim #2: A first, important step in securing your PC is to install and configure a NAT router.

(Note: I first posted this maxim nearly a year ago at Ask the Geek, Too. The article was entitled, How to Secure Your Computer: Maxim #2 (or, How Not to Invite Attackers Into Your PCs and Networks). Since then, many routers now contain built-in firewalls, so do double-duty and are even more secure.)

Next time: the one, most overlooked configuration option that can render your router or firewall useless and make you even more vulnerable than you were without it.

The Geek

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