Definition

• In the world of biology, a virus is a tiny organism made entirely of genetic code (that is, DNA or RNA) only capable of replicating itself within the cells of plants or animals. This is a good analogy for a computer virus, which is also made entirely of code and can only reproduce when it has a host computer. A computer virus is a program that, without the user's permission, runs in the background and tries to replicate itself. Viruses can replicate themselves by copying themselves to other computers on your network, sending themselves to other contacts in your email or instant messaging accounts or through any other number of ways. All these methods of propagation can use up your bandwidth and slow down your download, but this typically is not the case.
  
  

Payload

• What typically causes a computer virus to use up bandwidth is the "payload" of the virus. If the first thing a virus does after infecting your computer is spread itself to other computers, the payload is the second thing--essentially, the payload is the nasty thing the virus does to your computer after spreading itself. Sometimes, this payload is almost anarchical, destroying your files for no apparent reason. Viruses with this sort of payload became famous in the late 1990s to early 2000s for obvious reasons. Having your files deleted is something everyone would be able to recognize and fear. Today, most viruses are sneakier than this; typically, they have more practical payloads in mind. Some excellent examples of this are a DDoS (Distributed Denial of Service) attack and the sending of spam emails.
  
  

DDoS

• A DDoS attack is a method used by blackhat hackers (that is, a computer enthusiast willing to break the law) to shut down websites. Imagine if millions of Internet uses went to the same website and repeatedly pressed "Refresh," loading the site repeatedly. This amount of requests would eventually cause the server (the computer the website is on) to crash or sometimes even overheat, effectively shutting the website down until it can be repaired. A DDoS attack is essentially doing this instead of coordinating millions of humans on computers infected with a certain virus being commanded to begin the attack. The result can be devastating. One such attack in June 2009 temporarily shut down whitehouse.gov and some CIA websites, and was traced back to North Korea. Such attacks would also slow down any downloads you are attempting to make as they use up most of your bandwidth.
  
  

Spam

• Ever wonder where all that annoying spam in your inbox comes from? If you do not run a firewall or antivirus software, it might be from you. A common payload for computer viruses is the sending of spam emails. Some computers will actually send the spam from your computer, greatly reducing costs for spammers by lowering their overhead. Unfortunately, this particular payload can sometimes leave little bandwidth for you, causing your download to run slowly.
  
  

Strategy

• If you think you have a virus, there are steps to take to get rid of it. Antivirus software, free and commercial, is readily available (see link in Resources). Just as important as antivirus software, however, is common sense. Run a firewall and never allow programs you do not recognize to access the Internet. If you are not sure what a particular program is or does, look it up online. Do not download software from sources you cannot trust. Sources of pirated software are particularly infamous for not being trustworthy. Even if you do trust a source, scan the source before running it. And perhaps most importantly, do not do all your computing an an administer account. Use a user-only computer for everything except administration tasks like installing software.