I am Ben and I am in forth grade. I would like to know what a trojan horse is.

Well Ben, I notice that you said "a trojan horse," rather than "the trojan horse." That does make a difference in the explanation. First I'll review (in case you didn't know) what the trojan horse was, then we'll talk about how that phrase is used today in the world of computers.

Did you ever learn about the Trojan War? The Trojans were citizens of the city of Troy. The story of their war with the Greeks is recounted in Homer's Iliad, and other Greek literature. According to the story, the Trojans defended their city against the Greeks, but they finally lost when their enemies built an enormous wooden horse and hid a group of soldiers inside it. The Trojans thought it was a peace offering, so they brought it into the city and had a big party.

Then, in the middle of the night, while everyone was asleep, the soldiers climbed out of the horse and opened the city gates, letting in the Greek army. The Trojans were defeated because they were so gullible.

That's the trojan horse. But today we use that phrase to mean something similar, but different.

In computer terms, a Trojan Horse is a computer virus that is designed to fool people, just like the Trojans were fooled. It may be a program that is supposed to do something helpful, but really is also doing some unhelpful things.

Maybe you get an email that says "The attached file is an update from Microsoft. Open it to update your computer." Only, it's not really an update from Microsoft - it's a program that deletes all the files on your computer. But you believe the message, so you open the file. Now you're just like the Trojans. You thought you had something nice, but it turns out to be very nasty instead.That's a Trojan Horse.

Or you might be looking for a piece of software to do a particular job. Maybe you want some photo editing software, or screen capture software, or video conversion software. So you go looking online, and you find a free version of the software. You get excited about not having to pay anything, and you download it. But you don't realize that the software is actually spying on you, or damaging your computer in some way.

And by the way, that should be a good reminder to you of how cautious you should be when you download files from the internet, and when you open files attached to e-mails. Don't be like the Trojans - always be suspicious!

I'm kind of annoyed that after buying my AntiVirus software, the company is hitting me up for a "subscription renewal"? What in blue blazes is that, and do I really need to do it?

Yes, you need to keep renewing your subscription. It's one of the most painful expenses you'll face each year--not because it costs so much (all things considered, it really isn't so bad) but because it's a fee you have to pay for the malice and moral bankruptcy of the virus creators.

See, that yearly fee you pay helps to pay the costs of all the teams of computer geeks who are working to circumvent the viruses that are being cranked out on a daily basis. You may say "But it's not fair that I have to pay for someone else's deviant behavior." And you would be exactly right in saying that. It isn't fair.

But it also isn't fair to ask a software company to protect your computer from new viruses every day for free either. You see, every time a new virus is invented, some software developer has do design a way of capturing and removing that virus. And guess what! Software developers don't work for free, and we shouldn't expect them to! So, grin and bear it, and keep reminding yourself, not a penny of that money goes to the guy who invented the virus.

My AntiVirus software keeps talking about downloading "virus definitions". I don't understand what that means, or why I would want to do it. Can you explain?

When dealing with biological viruses, you want to have an antibody, which will either protect you from being infected or, if you've already been infected, it will start killing off the virus. But there isn't one antibody that works for all viruses, which is why scientists are always working to find new ways to combat new viruses. Computer viruses are very similar. A virus definition is like an antibody. It's really just information about a particular virus, which will help the virus software fight the virus, or protect you from infection. And just like each biological virus requires a different antibody, each computer virus requires a virus definition. Do you want to download the virus definition files whenever your computer recommends that you do so? Absolutely!

Good grief! What is up with this? My friend emailed me a database file, and Outlook tells me it won't let me receive it. Have any suggestions?

This may be moderately annoying, but it is in your best interest to have Outlook do everything it can to protect you from malicious code which may be hiding in database files and executable files. So you may not be able to open that MDB or EXE file your friend sent you.

But don't despair, you can get around Outlook if really need that file. Email your friend back and tell him "I need you to change the file extention to .MDX (or anything else besides .MDB) and then resend it to me."

Your friend changes the file extension, Outlook no longer recognizes it as a database file, and it lets it through. Now, when you save the attachment, you've just got to remember to change the extension back to .MDB and you're good to go!

2016 Update: This is not just an Outlook issue anymore. E-mails tend to get checked for potential viruses at every step along the delivery process. And some services are downright scary in how sophosticated their checking algorithms are. I have a client that I do VB.net development for, and occasionally they need me to update a single *.aspx file and e-mail it down to them. But their mail server rejects as hazardous any e-mail with the *.aspx extension.

No problem, right? Just change the extension to something like *.asz.

No dice; their server still rejects it.

Okay, so let's try zipping the *.aspx file. Nope. Still no joy.

Change the file extension, then zip it?

Their server is smart enough to still recognize as potentially hazardous.

Change the file extension, zip it, change the zip file's extension from *.zip to *.ziq. STILL no luck.

Give up and mail the updates to my contact person's personal e-mail address.