Software Threats

Software threats can be general problems or an attack by one or more types of malicious programs.

Software Problems

This category accounts for more damage to programs and data than any other. We're talking about non-malicious software problems here, not viruses. Software conflicts, by themselves, are much more likely threats to your PC than virus attacks.

We run our PCs today in a complex environment. There are many resident programs (e.g., anti-virus, video drivers) running simultaneously with various versions of Windows, DOS, BIOS, and device drivers. All these programs execute at the same time, share data, and are vulnerable to unforeseen interactions between each other. Naturally, this means that there may be some subtle bugs waiting to "byte" us. Any time a program goes haywire, there's the risk it may damage information on disk.

There's the further problem that not all programs do what we hope they will. If you have just undeleted a file, you don't really know if all the correct clusters were placed back in the right order. When SCANDISK or CHKDSK "fixes" your disk for you, you have no way of knowing exactly what files it changed to do its job. It becomes even more complex if you use other utilities to do similar tasks.

Software problems happen and can be very serious if you have not taken appropriate action in advance of the problem.

Software Attacks

These are programs written deliberately to vandalize someone's computer or to use that computer in an unauthorized way. There are many forms of malicious software; sometimes the media refers to all malicious software as viruses. This is not correct and it's important to understand the distinction between the various types as it has some bearing on how you react to the attack. The discussions that follow attempt to make clear distinctions between malicious software types. Realize that often a malicious program may have characteristics of more than one of these types (e.g., a virus that attacks files but also spreads itself across a network). Don't get wrapped up in the semantics, just try to understand the major differences.

In addition to viruses, the main thrust of this tutorial, there are (these three will open in a new window):

• Logic Bombs. Just like a real bomb, a logic bomb will lie dormant until triggered by some event.
• Trojans. These are named after the Trojan horse, which delivered soldiers into the city of Troy.
• Worms. A worm is a self-reproducing program that does not infect other programs as a virus will, but instead creates copies of itself, that create even more copies.

Finally, a type of malicious software that could be classified under Trojan but I've put on a page of its own as a special case:

• Virus Droppers. A dropper is a program that, when run will attempt to install a regular virus onto your hard disk.  

Summary

• Non-malicious software problems can be a significant source of problems and one should always know their computer's exact configuration to be prepared.
• Malicious software falls into several general categories:
  • Logic bombs
  • Trojans
  • Worms
  • Viruses