Virus, Trojan,Worm & Malware
Threats to a computer comes in different forms.  Each form is a different transmission method.  If you spend a moments of this page to learn the differences then you will be more likely to guard you and your computer from harm.
VIRUS:  Generally requires a human to click or activate it.  It is always a program file.  If you run an infected file, you just gave it to yourself.  The human is generally tricked into opening or running the file.  They are usually found in E-Mail attachments, files over chat (or messenger) programs, or a download from a rogue web site or popup page.  Biggest symptom is the file is an executable.  The executable means the file ends with (.exe) .  No one should run a downloaded files called   " DestroyEverything.exe " so it is probably not going to be named that.  Yes, actually you would if I trick you into it.

VIRUS TRICK:  A popup page that says your computer has a multiple virus and spyware, get this file and fix it NOW.  It is FREE.  Do NOT WAIT.
VIRUS TRICK:  I am sorry.  Before you can watch this movie you need to get the proper CODEX file installed.  Click HERE to download and install.


 
TROJANS:  These guys hide in other programs.  If you really like the word FREE and start downloading things called FREE, you will get a Trojan!  Another easy way to get is Trojan is to get of FILE SHARING NETWORKS.  Yes, mister pirate, downloading software, music, and videos that should cost something and you are not paying for then --- YET.  This will be an expensive song once you have taken your computer in for repair or reloading.  So what does a Trojan do?  They jump out of the file that you just downloaded that it was hiding in.  Now that they are looses then can do just about anything that someone programmed them to do.  Also, like the Trojan Horse, they open up and release their hidden cargo.  The hidden cargo can also be a virus.  The hidden cargo can be just about anything evil you can think of such as sending information about your credit card if you ever used it on the internet.  This threat does not need a trick.  It was hiding in something that is usually illegally downloaded or offered for free.  Trojans hide inside other programs and jump out the moment they are run.

WORMS:  This is one you can possibly do nothing and still get.  The easiest way to get a WORM is to have high speed internet (DSL or Cable) and to leave your computer continually on while connected to the internet.  This one worms it way around all the executable files (corrupting each with a copy of itself inside each) until it escapes through the network to get on other computers it can find.  Remember this, high speed internet is ALWAYS ON.  It does not matter if you are not playing on the internet -- it is still connected (if your computer is running) to a live internet feed.  The very best way to stop these is with a "router".  Everyone with high speed internet should have a router.  Only more advanced computer users will know how to manage a "firewall".  A router has a hardware firewall built-in to it -- and it does not make wrong decisions.  Every computer (even if only one) behind a router is secure from worm threats.  Yes, a really good firewall program will do the same -- except, novice computer users do not know how to properly use them and more often than not will prevent the internet or their own anti-virus program from working by making an incorrect choice.  A router is a right choice for almost every high speed internet user.

BLENDED THREAT:  Nothing more than a combination of any of the three above.  Many threats that are called "normal" are in fact blended.

MALWARE/SPYWARE/ADWARE (not Ad-Aware):  These are ill intent little programs.  A program that says it will remove the spyware from your computer but actually increases the problem now on a vast scale.  A program that says it will clean your registry and make your computer run faster but actually adds a hacker tool so they can monitor everything you type.  A program to decorate the skin of your music player that additionally adds the ability to track your computer on the Internet for an advertiser paying them for the information.  Yes, FREE software can be great.  Do remember that real FREE software is NOT BEING ADVERTISED, because there is NO money to be gained from it.
For a very detailed description of all threats.

Keep Your Computer Clean

Software Name Description Download Site Helps User Manual
Ad-Aware Cleans tracker "cookies" and advertiser data. Lavasoft Support Forum Tips & Helps
SpyBot S&D Removes hacker tools and immunizes most major threats. Safer-Networking FAQ's Tips & Helps
Free Surfer Stops Pop-Up web pages Kolumbus Support & FAQ's None
AVG Anti-Virus Grisoft FAQ's Guide
Threat Fire Higher threat and "root" kit protection. PC Tools Team On-Line Support Form Guide
Site Advisor Web surfing threat color warning. McAfee Community Forum None
Spyware Blaster Protects Active-X and prevents unwanted web site access. Java Cool Security Forum None

 
Router (wireless or not) is a wonderful security device.  Routers are like baby size computers that just happen to includc FIREWALL protection.  Unwanted (not requested) information that appears from the outside world is trashed if no computer requested the information.  Routers are recommended EVEN IF the user only has but one computer because of the security they offer.  Firewall software, for 90% of all users, is a great way for them to mess up their own computer.  Using firewall software requires the user to understand a great deal about their computer operation and how their software works.  If you are in the 10% then COMODO firewall software is one of the best on the planet and it is free.

SHOW ME REAL FREE SOFTWARE  MORE ON SECURITY TO KNOW