Do You Know — Digital Vermin

By Vangie Beal | Posted November 05, 2004

The most common blunder when the topic of a computer virus arises is that people will often refer to a worm or Trojan Horse as a virus. While the words Trojan, worm, and virus are used interchangeably, they are not the same. Viruses, worms, and Trojan Horses are all malicious programs that can cause damage to your computer, but there are differences between the three, and knowing those differences can help you to better protect your computer from their often-damaging effects.

Viruses
A computer virus attaches itself to a program or file so it can spread from one computer to another, leaving infections as it travels. Much like human viruses, computer viruses can range in severity; some viruses cause only mildly annoying effects while others can damage your hardware, software or files.

Almost all viruses are attached to an executable file, which means the virus may exist on your computer but it can't infect your computer unless you run — or open — the malicious program. It's important to note that a virus can't be spread without a human action, (such as running an infected program) to keep it going. People continue the spread of a computer virus, mostly unknowingly, by sharing infecting files or sending e-mails with viruses as attachments in the e-mail.

Worms
A worm is similar to a virus by its design, and is considered to be a sub-class of a virus. Worms spread from computer to computer, but unlike a virus, it has the ability to travel without any help from a person. A worm takes advantage of file or information transport features on your system, which allow it to travel unaided.

The biggest danger with a worm is its ability to replicate itself on your system, so rather than your computer sending out a single worm, it could send out hundreds or thousands of copies of itself, creating a huge, devastating effect. One example would be for a worm to send a copy of itself to everyone listed in your e-mail address book. Then, the worm replicates and sends itself out to everyone listed in each of the receiver's address book, and the manifest continues on down the line.

Due to the copying nature of a worm, and its ability to travel across networks, the end result in most cases is that the worm consumes too much system memory (or network bandwidth), causing Web servers, network servers, and individual computers to stop responding. In more recent attacks — such as the much talked about Blaster Worm — the worm has been designed to tunnel into your system and allow malicious users to control your computer remotely.

Trojans
The digital Trojan Horse of today is as full of trickery as the mythological Trojan Horse after which it was named. A Trojan, at first glance appears to be useful software but will actually do damage once installed or run on your computer.

People on the receiving end of a Trojan are usually tricked into opening them because they appear to be receiving legitimate software or files from a legitimate source. When a Trojan activates on your computer, the results can vary. Some Trojans are designed to be more annoying than malicious (like changing your desktop, adding silly active desktop icons), or they can cause serious damage by deleting files and destroying information on your system.

Trojans can also create a backdoor to your computer that gives malicious users access to your system, possibly compromising confidential or personal information. Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate.

Combating Viruses, Worms and Trojan Horses
The first step to protecting your computer is to ensure that your operating system (OS) is up-to-date. This is essential if you're running a Microsoft Windows OS.

Secondly, you should have anti-virus software installed on your system and download updates frequently to stay current on the latest fixes for new viruses, worms and Trojans.

Additionally, make sure your anti-virus program can scan e-mail and files as your computer downloads them from the Internet. This helps prevent malicious programs from ever reaching your computer. If this isn't enough protection, then you may want to consider installing a firewall as well.

A firewall is a system that prevents unauthorized use of, and access to, your computer. A firewall can be either hardware or software. Hardware firewalls provide a strong degree of protection from most forms of attack coming from the outside world. You can buy one as a stand-alone product or as part of a broadband router. Unfortunately, when battling viruses, worms and Trojans, a hardware firewall may be less effective than a software firewall, as it could possibly ignore worms embedded in out going e-mail — viewing it not as a threat but rather as regular network traffic.

For individual home users, a software firewall is the most popular option. A good software firewall will protect your computer from outside attempts to control or gain access to your computer, and it usually provides additional protection against the most common Trojan programs or e-mail worms. The downside to a software firewall is that it only protects the individual computer it's installed on, not networked PCs.

It is important to remember that, on its own, a firewall is not going to rid you of your computer virus problems. However, when used in conjunction with regular operating system updates and a good anti-virus scanning software, it will add extra security and protection for your computer or network.

Adapted from Webopedia.com.

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