You're in big trouble. If your IT department isn't security-crazed, or if you take work home, you're vulnerable to teenage vandals, clever hackers, Eastern European zlorgs, people you once fired, commerce-hating hippie wackos, script punks, desperate competitors, random anonymous thrill seekers, credit card chiselers, data vacuumers, and crackers running powerful scanning software that probes your system for weaknesses, flimsy passwords, and gaping security holes.

In the past this was a big yawn. Most users were either connected to safe local networks or ran as stand-alone systems with an occasional brief dial-up connection to read their mail. Besides, there wasn't much on their hard disks worth stealing.

Not today. Users are switching to persistent Net connections like cable modems and DSL. They're running their systems 24 hours a day, leaving themselves wide open to assault. They're doing e-commerce, investing, bill paying, taxes, and other financial transactions online, all of which litter their systems with valuable passwords, credit card info, account numbers, and personal data.

And they forget that the Internet works both ways. You know how fast and easy it is to get onto Web sites all over the world? It's just as easy for creeps and scam meisters all over the planet to get into your digital pants.

This wouldn't be a big deal if break-ins were difficult and security was robust. Unfortunately, you're easy prey, and if you don't bolt things down fast you're toast.

Here's why: Windows 95/98 security is a joke. Win NT/2000 is better but far from perfect. Kids armed with the new crop of automated port and file-share scanners, password crackers, and IP probers can methodically bust their way into thousands of systems a night. Including yours.

Want to get your adrenaline pumping? Run the intrusion-monitoring modules that come with any of the better personal firewall packages, and count the number of scans and probes trying to invade your system each day. It's typically in the dozens.

Even if intruders don't steal anything, they can find out lots of personal information about you, scramble your files, or even use your system as a base for attacking other systems—which is how they shut down Yahoo, eBay, and E*Trade in February.

You have three defenses against break-ins. The first is to plug the leaky parts of Windows. The second is to install a strong personal firewall. And the third is to use the password features of your system properly.

Most users don't bother with passwords on their home systems, since these slow you down (or worse, stop you cold if you forget them). Users pick simple words that are easy to figure out, and don't ever change them. But brute-force cracking programs throw entire dictionaries at your system. So pick longer combinations of numbers and letters, and change these at least every month.

Good firewalls are cheap (30 bucks or so) and effective. But clumsy ones can actually call attention to your system and encourage break-ins because they make it look as if you're protecting something valuable.

Finally, plug the porous network and file-sharing holes in Windows. Doing this will seal a gaping security hole and, as a bonus, speed things up by conserving system resources.

There will still be chinks in your system's armor, and clever hackers can bust in through chat, e-mail, or lots of other ways, but at least you won't have your front door wide open with a sign on the lawn guiding them in.

To learn how to protect yourself, and to safely test your system for leaks, check out Steve Gibson's terrific Shields Up page at https://grc.com/x/ne.dll?bh0bkyd2. You'll be glad you did.

E-mail paul_somerson@zd.com