Crouching Trojan, Hidden Malware

Trojans are not just more dangerous than computer viruses, they're stealthier, too. Find out where they hide.

Minions of an evil master lurk in your hard drive, crouching in your system registry, ready to pounce.

What Is a Trojan?

The word "Trojan" is a mystery to most people, even many who think they know its true meaning. If more people really understood what Trojans are and the risk they pose, there would be fewer Trojans, since fewer people would ever leave their machines vulnerable to them.

A Trojan is malware. Malware is a special kind of software, like spyware, adware, and viruses that no one wants. Yet a Trojan is more dangerous than any other kind of malware. Unlike those other types of malware, Trojans are not mindless flunkies hurled at your computer by their masters. A Trojan is a master that first craftily infiltrates your PC, then unleashes its malware henchman.

What Trojans Do

• Some Trojans may install worms, which are programs that use your computer and internet connection to send out armies of server requests in the hope of shutting a particular website down, or to spread viruses or worms to other computers.

• Other Trojans are thieves, out to steal your computer's processing power and turn it over to their hacker masters, often by setting up a backdoor, a hidden internet connection that allows for outside manipulation of your machine.

• Some thieving Trojans are fraudsters that may go after your financial information by installing keyloggers that record what you type--especially passwords and important banking numbers.

How Do Trojans Hide?

No one thinks they have a Trojan on their computer until it is too late. That's because they do such a good job of blending in.

• Trojans come disguised in innocuous file names, often pretending to be a helper application to software or an essential operating system component.

• Trojans try to avoid calling attention to themselves, and so will often only interfere a little, if at all, with your computer's performance, choosing instead to do their dirty work while your machine is idle. Computers left on and connected to the internet while their owners are asleep or at work or school are favorite targets.

How Do You Remove Trojans?

Removing Trojans can be a can of worms. Here's why you need to proceed with caution:

• Since Trojans can disguise themselves as software your computer actually needs, you could accidentally delete a vital program or system registry entry. In the worst case scenario, you won't be able to restart your computer.

• Many Trojans are trained for survival. When you try to removal them manually, they may simply copy themselves to another directory.

Intimidated? You don't have to be. Rather than trying to defuse a Trojan yourself, why not call in the bomb squad? Good anti-spyware and antivirus software will fight Trojans, too. Just make sure to look for a program that specifically says it fights Trojans. After all, this is no job for amateurs.