Many similarities exist between viruses and worms but there are some differences. For example, a virus is designed to spread from file to file in a single computer. Even though it has full reign to infect the entire computer it really does not attempt to spread on its own. When people use infected computers to send e-mail attachments, share files (like music in a file sharing peer-to-peer network), burn files on a CD for a friend or basically move an infected file to another computer the virus will ultimately spread. A worm, on the other hand, infects without user intervention due to vulnerabilities found in software. Imagine all the files and programming code written to make a computer operating system work. Thousands of programmers work countless hours writing this code. Now imagine how difficult it would be to make sure every potential security flaw was fixed. It is similar to an automotive manufacturer trying to find every problem with a newly designed car before it is released to the market.

Worms are released to attack computers through this type of security flaw also known as a hole. So just having an Internet connected computer turned on makes it susceptible to infection. Once infected, the worm takes over the computer, residing in active memory, eating up resources and using it as its new headquarters to infect other computers on the Internet. It can travel much faster than a virus. Individuals who create viruses and worms do so just for the sheer challenge and fun of exposing vulnerabilities in software companies' products. Sometimes it is in retaliation to some that monopolize the market with their overpriced software and untouchable mentality.

Software companies attempt to stay one step ahead of worms by finding their own holes and releasing patches or updates to fix them. Other times it is due to a frantic race to plug an exposed hole. Many companies also make virus protection software that can perform file scans and provide real time protection from threats as they happen.

Trojans
Trojan programs also known as Trojan horse programs are usually listed under the malware umbrella but operate much differently than their virus and worm counterparts. Named due to their stealth nature they pose serious threats to networked computer systems. Trojan programs are placed inside of or masked to look like useful non-threatening programs like screen savers, games, music, etc. Once the program is installed it can open secret access to a computer for rogue Internet users to come in and access files. It can also steal personal information from files and send it to a specific location on the Internet. All of this happens without the users' knowledge.

Infection Symptoms
If you wonder how you will know if a computer has been infected with a virus or worm here are some common characteristics of infection.

- Sluggish or unusually slow operation
- Tends to become unresponsive or lock up often
- Crashes and reboots repeatedly
- Menus and boxes look distorted
- System drives are not accessible
- Printing is not normal
- Strange error messages
- Programs seem to hang and act strange

Antivirus Software
As the name indicates, antivirus is a program designed to protect a computer from viruses by scanning files on a scheduled basis. In addition, it also auto-protects by examining new files in real time as they are used. For antivirus to be effective it must be updated with information about the latest threats. Antivirus companies make update subscriptions available on their web site and the program can be configured to check the site and download them. Updates can also be updated manually by selecting an update icon found in the program. Subscriptions only last for a year from the date the program is installed. After that, subscription renewals are available for purchase on a per year basis. Some users renew over the Internet with credit card while others purchase the program each year at the store.

Most computer manufacturers install trial versions of antivirus on new computers. After a 90-day trial the subscription can be renewed as normal. However, if a user wishes to use their own program, it can be removed completely. Various antivirus brands and options are available. Most are reasonably priced while others are free for Internet download. Free versions are not limited by renewal and can be just as effective. Many times antivirus producers offer free stripped down versions of their flagship program to entice users to purchase the real one.

Some free Antivirus websites.
http://www.grisoft.com
http://housecall.trendmicro.com
http://www.free-av.com
http://www.pandasoftware.com/activescan
http://www.avast.com/eng/download-avast-home.html

Some regular Antivirus websites.
http://www.mcafee.com/us/
http://www.pandasoftware.com/
http://www.sophos.com/
http://www.symantec.com/
http://www.sarc.com

SPYWARE

Spyware is software that spies on a users Internet activities. This can include personal information entered such as credit card and banking numbers as well as web site visits. The information is gathered and transmitted over the Internet to a receiving source. This happens without the users knowledge as it uses their computer's resources for its own purpose. This information is also gathered for target marketing. Spyware is notoriously associated with Internet use although some forms are more malicious than others. Often it is included with software users actually want to install such as Internet games, Instant Messaging and file sharing programs. When installing these programs, users blindly click through configuration screens without realizing what they approve. The information can also be presented in a confusing way essentially tricking the user to agree thinking they did not. There are even times when users knowingly download and install spyware because they are persuaded to think it is a useful utility. Programs like web accelerators, Internet toolbars, coupon generating and weather monitoring are usually forms of spyware. One spyware program targeted at teenagers will place an animated gorilla on the screen that talks to them and offers searching suggestions while online. It also tells an occasional joke and makes silly faces. The whole time the program is spying on everything they do.

Adware
Adware in some ways can be like spyware but is differentiated because it focuses more on displaying advertisements rather than tracking users. For example adware can be included with free versions of software downloaded from the Internet. Typically users are subjected to advertisements when using such software. A users Internet activities can also be tracked in order to provide real-time advertisement based on the particular subject matter they are viewing. In addition to adware, free software can also include tracking software like spyware. In such cases the user installation agreement will reveal this in the fine print but most users fail to read it. Therefore tracking software, which should be classified as spyware, is not because the vendor informed the user they would be tracked.

Anti-Spyware Software
Some antivirus programs also include spyware removal features. There are, however, other stand-alone programs that exist solely for this purpose. Since adware can also be considered spyware, the programs work to remove it as well. Just like antivirus, these programs can also be configured for auto-protection and routine scans but must be kept updated.

Some Anti-Spyware websites.
http://www.lavasoftusa.com/software/adaware/ (Ad-Aware)
http://www.safer-networking.org/ (spybot search and destroy)
http://www.trendmicro.com/spyware-scan/
http://www.javacoolsoftware.com/spywareblaster.html