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Most computer users are aware of the dark side of the Internet. Our online world brings issues of credit card and identity theft, junk mail and seedy content right into our homes and offices. But how many computer users are unwitting accomplices to such activities?

Your computer, or those of the people in your organization, is possibly being used to send spam, harvest e-mail addresses for spam, make purchases using stolen credit cards or take part in a denial of service (DoS) attack, where an army of computers shuts down a Web site by flooding its servers with HTTP requests.

EarthLink's SpyAudit program, which scanned 1,062,756 PCs, found 29.5 million instances of spyware, an average of nearly 28 spyware items per computer.

How does this happen without your knowledge? Examples like those above are usually the work of a trojan, a small program that can be unknowingly installed on a computer and then accessed by another computer over the Internet. Together with programs called spyware, adware and viruses, trojans are a part of a group collectively known as "malware" or "pestware." While the majority of such programs are pests and nothing more, they have the potential to be quite nasty.

Trojans: RATS That Can Control Your Computer

Like the horse of old, a trojan carries with it an unexpected surprise. Trojans do not replicate like a virus, but they do leave behind a program that can be contacted by another computer. From there, they can do just about anything. While it's possible a trojan can be used to take control of a computer, the most common trojans are dialer programs. Dialers are used without your knowledge to make international or premium calls (900-type numbers) from your PC. That's more than an annoyance; it can get expensive.

Trojans are also known as RATS (remote access trojans) and they are most often hidden in games and other small software programs that unsuspecting users download then unknowingly execute on their PCs.

Two common trojans are known as Back Orifice and SubSeven. Back Orifice was originally developed as a remote administration tool. But it worked by exploiting holes in Microsoft software, which makes it a popular tool for nefarious applications. Both Back Orifice and SubSeven can be used to capture what is on a computer's screen and what is typed in using the keyboard; they can be use to remotely control devices, such as opening and closing the CD drive; or to set up FTP, HTTP or Telnet servers on an unsuspecting user's machine. Basically, anything that can be done with a computer can be done remotely using a trojan.

Spyware: Who's Watching Your Online Moves?

Spyware programs range from annoying to the dangerous, including keyboard loggers and screen capture applications that can steal passwords and other sensitive information. The programs are sometimes bundled in with shareware or freeware programs that can be downloaded from the Internet. Often times they claim to be helpful utilities that also carry a more sinister side.

Many of the programs are marketed as legitimate tools for keeping tabs on children and spouses online. One program called Activity Logger, for example, connects to the Internet on its own, records the URLs of sites visited and the keystrokes from e-mail and chat applications. It will also capture screenshots that can be made into a slide show.

If you find Intranet Journal's Spyware Guide helpful, try InsideID's Identity Theft Prevention and Recovery Guide

Adware: Caught in a Marketing Nightmare

Adware is software that displays advertisements to computer users. Some of the most strict definitions of adware include applications that are sponsored for their free use. One of the most popular examples is WeatherBug, which offers a free version of weather software and comes wrapped in a skin that displays advertising. While older versions of WeatherBug had rather significant privacy issues, newer versions are pretty straight forward: you see the ad, but you get the weather. Is this adware? In the most strict sense, many people say it is. But to some computer users, the tradeoff seems fair. Hotmail, Yahoo Mail and AOL's Instant Messenger are among other software programs and services that display ads to their users in exchange for free usage. Many of these programs off advertising-free versions for a price.

More infamous among adware watchers is Gator, which now goes by the name Claria Corp. Gator was controversial from the start. It began in 1998 offering e-wallet software. But it reports your Web surfing habits back to its parent company, which then sends you advertisements targeted according to your data. The vast majority of people consider it a pest, especially because the software is often bundled with other, more useful software. As annoying as it is, Gator is not very malicious.

As for adware that reports personally identifiable information, once again tolerance varies. Some people don't want any information, such as tracking the sites you visit, revealed. Others draw the line at logging IP addresses.

Viruses: Contagious Pests

For all the publicity viruses have gotten, they remain a serious threat. While viruses can potentially destroy a computer's data, most of the widespread viruses have leaned more toward annoyance. The most famous are e-mail viruses that replicate and spread using e-mail addresses stored on a computer. They still cost computer users and their employers hundreds of millions of dollars annually.

The MS Blaster worm that caused havoc in the summer of 2003 exploited a vulnerability in the Remote Procedure Call (RPC) function of the Windows operating system. Anyone who did not install a patch issued by Microsoft was vulnerable, marking a new era in virus prevention for many Internet users. No longer was using care with e-mail attachments enough to keep you safe.

Next Page: Symptoms of Spyware and Other Pests

Questions, comments, additions for the Spyware Guide? Contact editors@intranetjournal.com

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