Explanation

Firewall- a piece of software or hardware (also router) that prevents hackers or malicious programs from entering your computer via backdoor access- also keeps unauthorized programs from sending data out.

OS (Operating System) update- your Windows or Mac Operating System needs occasional updates to correct any security flaws that are discovered.

Computer virus- a name for any variety of malicious programs that take residence in a host computer.
Virus is the over-arching term that includes:
TROJAN HORSE: programs disguised as one thing but really act maliciously behind the scenes
WORMS: programs that propogate by themselves using your computer and Internet access as the medium for other infections. Worms can also install malicious programs on a host computer.
SPYWARE: Programs that keep track of your computer habits: some send data to marketing firms, others send a record of all your keystrokes (including passwords) to identity thieves.

File sharing is a Windows feature that allows for access between networked computers. For example the computer in your office could access the hard drive of the living room computer if they are networked. Sometimes this setting is used by remote computers to access data over the Internet.

Peer to Peer Programs- otherwise known as file-swapping programs, Napster was the first to hit the popular scene for music (mp3 ) sharing, now people swap software, video, and image files. Most of these sites are unregulated, so virus writers will post a new virus, label it as something appealing (music, video, image) and an unsuspecting file-swapper will run the program and wonder how his computer was infected

The presense of broadband Internet access (Cable, DSL, etc) makes virus protection even more important. With constant connectivity to the internet, a computer becomes a much bigger target for viruses that scan internet addresses (IP addresses) to find victims. Once infected, an always-connected computer can work 24/7 to spread the virus to others.

A wireless home network (aka wi-fi or 802.11 a, b, or c) needs to be secured so others can't use your bandwidth for their own surfing or wriggle into your computers via wireless access.