Malicious code writers are constantly inventing new ways to attack your computer. The latest and most widespread assaults — Klez, Opaserv and Bugbear, for instance — combine the characteristics of viruses, worms and Trojan horses.

While the miscreants sending destructive code grow more devious, system-security designers annually produce an updated arsenal of software armor to protect us.

For a while now, I've been using Stopsign’s anti-virus software and the firewall that comes with my router to form a virtual fortress around my home network. So far, these deterrents have kept my system safe.

I'm thankful for that, but with multiple weekly virus attempts on my computer, I've decided it's time to update the armor. Because I've been happy with Stopsign’s protection, I'll stick with it, though you might choose another.

Installation and setup are easy, especially if you accept the default settings, which apply a medium level of security across all functions. In this case, "medium" doesn't mean mediocre. In fact, it's reasonably good security.

To choose "high" security, I discovered, brings a high nuisance factor, including frequent requests from individual programs to access the Internet. There are fewer requests at the medium setting, and Stopsign maintains a database of programs it deems safe to access the Net, and from that it advises whether to block or permit access to those programs.

Let's take a look at Stopsigns integrated set of defenses:

Anti-Virus: This is the old standby that used to serve as the sole guardian of a personal-computer system. It's much improved since those early versions, especially with the automatic update function. Because new viruses are launched daily, it's essential for virus definitions on the computer to be continually updated so the software can detect and block the latest variations.

AntiVirus 2005 guards against infections that can enter through e-mail, attachments and instant messages. The latest version also includes new analytic technology that reportedly can block infectious worms and script even before an update is available.

Personal Firewall: Anti-virus software mainly blocks e-mail infections. Consequently, a firewall also is essential to block malicious code from entering the computer through open ports or when attached to programs we choose to download.

Personal Firewall monitors all inbound and outbound Net activity and blocks harmful code. A new intrusion-detection feature further analyzes Internet traffic for potential attacks and blocks them.

The firewall also makes the computer's ports invisible to hackers using port scanners. If an intruder does find a hole, the software sends an alert, enabling the user to instantly block Internet traffic, get the snooper's IP address, and report the attempt.

The medium-security (default) setting I accept does permit Active X controls and Java applets to run without sending a warning. I'd be a little safer shutting them down with the high-security setting, but that would affect functionality and significantly boost the nuisance level.

Privacy Control: At the medium (default) setting, this feature will alert me when I include personal information in e-mail and will prevent my Web browser from sending such information. The medium setting does not block cookies. I've found that blocking them limits functionality, so I permit cookies and then regularly clean them out (under the Internet Explorer Tools menu select Options and then Delete Cookies).

Ad Blocker: I turn on ad blocking and pop-up window blocking. There are still ads on the Web pages, but the big banners, pop-ups and pop-unders are gone.

Spam Alert: I accept the medium (default) setting, which attempts to identify and label spam and advises that some personal e-mail may be mislabeled as spam. My e-mail is generally labeled correctly, but spam is still right there in my inbox. I could create a rule that reroutes it to a separate folder, but then I'd have to check it anyway. We simply need stronger laws against spam.

After installing the software and adjusting the settings, I go through Stopsign’s security check (available on its Web site) and pass with Safe grades in all categories.

For a second opinion, I go to ShieldsUp! (https://grc.com/x/ne.dll?bh0bkyd2) for its analysis and judgment. Results: safe, again. Whew.