We are more connected than we think. My recent experience proves it.

Last week, I made the short trip to the nearby university, where I could work in peace using my portable electronics gear. I go there often; so I know where the power outlets and wireless networks are, and where to find the quiet nooks and crannies for productive work.

Over the past few years, my palm-sized PDA, not my laptop, has become my portable system of choice. But occasionally my laptop suits my purposes better because it has a large screen and mouse (which makes drag-and-drop easier). On this trip, I brought my laptop.

That laptop is vintage 1999. It's a workhorse for me that I normally use to create complex word processing documents or give presentations. Being six years old, it's only one-eighth as fast as most new computers. The central processor in my PDA is just as fast as my laptop; but my PDA is not slowed down by virus scanners, firewalls and other bothersome always-running software. On the other hand, extraneous devices and software slow my laptop to a crawl. Any time I can turn off the overhead, I do -- safely, of course.

On this day, after picking the perfect work spot, I removed my network card, plugged in my system, and powered it on -- after which I immediately turned off my automatic virus protection and any other software that could take away valuable computing speed.

I rarely turn off my virus protection -- because I'm the ultimate paranoid user. (Ask my family.) But with my network card unplugged, what could happen? Even with lots of students in the building with various types of laptops and PDAs, how would they access my system?

A few minutes after starting work, I needed to check a fact, which was conveniently stored on my PDA. So I pulled it out, checked my fact and then put it on the table next to my laptop.

Much to my surprise, an icon popped up on my laptop screen telling me that another computer had connected, and asking me whether I wanted to send files to the other computer. Did somebody figure out a way to attack my system without a network card being attached?

I immediately picked up my PDA to check it out, and found both Wi-fi and Bluetooth, the two wireless connection features, turned off. Besides, my laptop doesn't do Bluetooth, and my Wi-fi wireless card was not inserted.

Amazingly, the PDA and laptop were connecting via infrared technology -- the way that most PDA users beam business cards to one another. Normally, you must aim the infrared beams of the two devices at each other to get a connection. It's very short-range and very directional. Yet, my PDA and laptop were able to get reflected signals when they were close but not aimed at one-another.

Could that mean other users can connect to my laptop by infrared beams without me knowing? While a long shot, it looks like it is possible, requiring us to be wary of yet another way our system security can be breached.

My experience suggests that we must know our systems well. I knew I had the infrared beam in my laptop; but I've used it so infrequently, I consider it pretty useless and frankly forgot about it.

Computer vendors like to pack in features. You may have an infrared beam, Bluetooth transmitter or other connectivity feature that you don't know about. The best way to find out is to check your system specs. Then turn off what you don't use.