Viruses

The term ’computer virus’ has gone through various changes of meaning throughout the evolution of computer technology.  Regardless of the definition, a virus is malicious in that users have no choice about it in the event of infection.  In the most general sense, a virus is an executable code that seeks to replicate on a host system and spread to other computers through various means of transmission.  Before the widespread use of the Internet, the term ’virus’ was used for malicious code that was spread through floppy disks, as this was the only means to transmit data.  Now, viruses have taken second place to the new wave of ’worms’ that propagate through networks without the need to infect host files.

The severity of viruses and worms can vary from completely benign to overtly damaging.  In the worst case, a virus or worm can completely disable a computer.  Milder cases will reduce a computer’s overall performance by using up valuable system resources.  Weak viruses tend to have poor code that won’t affect your system at all.

Traditional Viruses

The traditional virus requires the user to execute a program that is already infected.  Transmission usually occurs through a downloaded program or macro.  For instance, you might download a game or application and attempt to run it.  If it’s infected, the virus will load into your system and begin propagating to other files.  As the virus spreads, the computer’s performance will begin suffering as a result.  Older viruses don’t use executable programs as their host.  Many old viruses infected the ’boot sector’ of a floppy disk.  For this type of virus, a user would have to attempt to boot his or her computer from the infected floppy disk.  From there, the code would be executed and the virus would infect the system.  Today, viruses are not such an immediate threat due to advancements in anti-virus software.  A careful user can avoid a large majority of viruses simply by scanning suspicious files before they are run.

Worms

On the other hand, worms have become the dominant form of computer infection since the dawn of the Internet.  Worms do not require host files to infect.  Rather, they take advantages of vulnerabilities in browsers and e-mail programs.  Once you’ve received a worm (usually through e-mail), it can open ’back doors’ in your system to effectively co-opt your computer for its own use.  Worms tend to make copies of itself and send those copies to other computers by using your e-mail software.  For instance, a worm may send itself to everyone on your contacts list without your knowledge.  Because of this feature, worms are known to seriously bog down the Internet when they reach their peak activity as millions of e-mails may be sent as a result.