If you have a broadband Internet connection such as a digital subscriber line or cable modem, the good news is that you probably enjoy full-time high-speed access to the Internet. The bad news is that someone else could be enjoying access to your computer.
Having an always-on connection to the Internet increases your risk of being hacked--anything from a harmless prank to the destruction of data on your hard disk. But there are safeguards that can protect your machine from invasion--including some that are free.
People who log on to the Internet via a standard dial-up modem are not totally immune from someone peering into or damaging their machines, but the odds of an incursion are much lower. Windows users who have a broadband connection and share their files with others on their local area network are more vulnerable because current versions of Windows make it possible for even unsophisticated hackers to gain access to your hard drive.
I found that out about a year ago when I gave Steve Gibson, president of Gibson Research Corp., permission to break into my PC. I told him my Internet protocol, or IP, address--something he could have figured out on his own--and five minutes later, he had complete access to my machine.
He told me the names of several files on my hard drive. Then he planted a file on my Windows desktop. It was an innocuous text file, but it just as easily could have been a virus or a "Trojan horse" designed to destroy files or invade my privacy. Then Gibson showed me how easy it is for someone to do just what he did.
Gibson's Web site, http://www.grc.com, includes several free utilities to test whether your machine is vulnerable. One utility, Shields Up, probes your PC to see just how open you are and reports that to you. After running that program a year ago, I closed the holes it exposed.
And just when I thought I was safe, Gibson came out with another utility, LeakTest, that gave me some fresh bad news. It turns out that my machine--and probably yours too--is wide open to a Trojan horse type of invasion that, if running on my computer, could send confidential data from my PC to a hacker anywhere in the world. Fortunately, this vulnerability can be prevented.
The way you protect yourself against hackers is to put up a firewall between your computer and the Internet. This doesn't prevent you from accessing the Net, but it does prevent unauthorized people from accessing your PC.
A firewall can be hardware or software. If you have a network, you might already have a piece of hardware called a router, which will prevent hackers from breaking in. This isn't the same as a network hub or a cable or DSL modem, so don't assume you're protected unless you know you have a router with a built-in firewall.
As I found out after running LeakTest, even if you have a router, you're not safe from a Trojan horse that sends data from your PC to someone else. For that, you need firewall software that blocks both unauthorized incoming and outgoing traffic between your PC and the Internet.
One of the best firewall programs happens to be free. ZoneLabs, at http://www.zonelabs.com, offers a free version of its ZoneAlarm firewall software to individuals and nonprofit organizations. The company sells a more sophisticated version, ZoneAlarm Pro, for $39.95 to businesses and individuals who want to be able to customize their level of security.
ZoneAlarm blocks all programs that try to access the Internet, but you can tell it to let certain ones through. You'll, of course, authorize your browser and e-mail program to access the Net. But if a program you're not sure about tries to access the Net, you can click "no," which blocks that program from sending or receiving data.
ZoneAlarm also blocks access to your PC from others and provides a log showing you whether anyone has tried to probe or invade your machine. It's free insurance and well worth the few minutes it takes to download and install the 1.7-megabyte file.
Another solution is to turn off file sharing or configure Windows so that file sharing is available to people on your network but not available via the Internet. Information on how to do that can be found at http://www.grc.com/su-bondage.htm.
Technology reports by Lawrence J. Magid can be heard between 2 and 3 p.m. weekdays on the KNX-AM (1070) Technology Hour.