A few years ago I boarded a bus in a small town in Colombia.

A man got on and began offering a food product to the passengers. Down the aisle he went, handing one item to each person on board.

When he finished, he went around and asked each person for one of two things: money or the item back. His idea, I suppose, was that once the product was in a prospect's hands he or she would have a harder time resisting it. (In my case, his strategy worked.)

Apparently this aggressive marketing tactic is now being deployed on the Internet. I turned on my computer one day and a few new program icons appeared. One of the programs running was a calendar-reminder. I figured it must be related to Microsoft Works, which I was using already, so I opened the program. Up came a screen that neither looked like Microsoft Works nor contained any of my reminder entries. I scratched my head and wondered where this program had come from.

Now, other people do use this computer. I checked with them. Did anyone download anything? The answer was a resounding and unanimous No. So I looked at Start>Programs>Startup. New programs had been added to the computer startup menu. Suspecting we'd been infiltrated by malware — that's short for malicious software — I ran Ad-Aware by Lavasoft (available at www.lavasoftusa.com) and, sure enough, it detected a malicious program at work.

What made this program malicious? First of all, it was installed on our computer without our asking for it, either by e-mail or Web browsing. Second, this program then began downloading other programs and installing them on our computer, again without our permission or even knowledge, bypassing even our Internet firewall. The calendar-reminder program seemed to have caused no particular damage. But what other programs, and from whom, would it download next?

Here's the thing. The programs the malware downloaded seemed to be free and useful — but the way they were foisted on me did little to endear their marketers to me. Yes, the “Colombian bus” approach worked on me when the product being peddled was food. But software is no little snack.

I also know that one aim behind many a sneaky installation is to set up programs that track where you go and what you buy on the Internet. This information is of great value to companies that want to market products and services tailored just to you. Unlike viruses, which are nothing but mischievous (albeit sometimes maliciously so), “spyware” is out to set you up as a target for sales pitches.

Once I removed the malware with Ad-Aware, I further had to uninstall all the other programs that had been installed unbeknownst to us. Nothing new has appeared since the housecleaning; however, I had another experience on a different computer similar to malware.

I opened Internet Explorer one day to discover a “search bar” added to my usual Explorer toolbar. It was not a command icon I recognized. And, as you might have already figured out, I don't like things changing on my computer without my consent. And I know that “add-ons” to Internet Explorer make up the majority of crashes in the browser program. The new search bar not only looked different, but it also used a search engine I had never heard of before. I decided to get rid of it.

On Explorer I went, opening View>Toolbars. Normally you can uncheck a toolbar and it will disappear. In this case, all toolbars listed were grayed out, meaning they were unavailable for selection. Next I looked at Tools>Internet Options>Advanced. I unchecked “Enable third-party browser extensions.” This took away the toolbar.

Still concerned that this unknown toolbar software might be lurking on our hard drive, I went into the Windows Registry and searched for the toolbar name. It appeared several times. My first impulse was to delete those registry entries. But I feared doing so might mess up Explorer.

I went to the Web site used by the search toolbar and clicked on the FAQ (frequently asked questions) section. Sure enough, others wanted to uninstall this thing. The company claimed that if Explorer had been altered, it was because the customer wanted the change. I never wanted it. I was fortunate, though, as I was able to download a program that promised to uninstall this toolbar — and it actually worked.

Microsoft has noticed that certain people are exploiting Windows and Explorer. Some “holes” malicious hackers use were meant to be helpful, such as Explorer add-ons. The Windows XP SP2 update contains many security enhancements and feature additions for Explorer. I encourage you to download it, as the new Web browser will offer a “Manage Add-ons” feature. Any add-on to Explorer can be easily disabled. It will include an advanced popup blocker along with a download blocker that will analyze attempted downloads and determine whether they were the result of user choice or some stealthy “push” from the outside. In the latter case, the toolbar will notify the user of the attempted download and offer the opportunity to make a decision. And Explorer will be set to the highest security settings by default.

With current versions of Windows, security settings are scattered all over. The Windows XP SP2 update will have a single security-control panel. Red and green lights will indicate the security level of individual settings.

It is hoped Microsoft will make these updates available to other versions of Windows as well. All this added security should make Internet surfing what it was meant to be: useful, informative, fun — and free of “Colombian bus” sales schemes.

Brother John Raymond, co-founder of the Monks of Adoration, writes from Venice, Florida.