In this modern Information Age, computers are necessities in life. Whether we use them for simple functions such as typing our homework and business reports, up to more important acts like online business meetings and transactions, one cannot deny that computers are a big part in our daily lives. Using a computer, particularly the Internet, is one task that even a ten year old can do at this particular period in time.With the growing increase of popularity and reliance on computers, as well as the demand for it, security risks have also gone up, which is a reality that cannot be ignored. With the billions of information bits being spread across the World Wide Web, hackers and computer intruders (criminals) see the value in focusing their attention to computers and the Internet. The information they would retrieve here is (more often than not) more useful than when doing it the old-fashioned way.As such, these intruders have devised some methods into getting information out of computer users, with or without these people knowing that they’ve been hacked into. As is the case in real life, there are some computer programs that are disguised to be innocent, but actually act as spies, providing information to the intruders. These malicious programs which are security threats are called computer viruses.Computer viruses should not be taken lightly. They work in many different ways; one of them may be to provide data to the one who planted the virus. Other viruses can simply be annoying - slowing down your computer, building unwanted files, etc. – while some can be very disruptive, such as deleting your hard drive, compromising your operating system, etc.As such, there are different types of viruses which normally differ in how they function and how they are spread. Examples of these include Trojan horses, worms, email viruses, and logic bombs. It would be important for you to know these kinds of viruses in order to better protect you from them, as well as to have the proper programs to get rid of them.Trojan horses are simply computer program that cannot reproduce themselves, but can do damage anywhere from minimal to extremely dangerous. It usually disguises itself as a common file (maybe an .mp3 music file or a .jpeg picture file) but does the damage when the computer user opens it. This is why you should take extra care when opening a suspicious looking file – it could very well be a Trojan horse.Worms are self reproducing programs that mainly use security holes in order to spread itself throughout the network. If your computer is infected with a worm and is able to replicate itself a number of times, this usually causes your computer to slow down noticeably since it uses your computer resources and memory to do so. They often use security flaws in operating systems (such as Windows) in order to self reproduce.Email viruses are self explanatory – they spread via email. Once a user opens the infected email, what it usually does is send itself to other computer users via the email addresses found in the user’s address book. Because it uses email and a lot of people open emails without really checking or being careful, it spreads very quickly across the entire world and can cause chaos within just a few days.Logic bombs are viruses that target specific computer applications, causing them to crash (for example, Windows). This can also be spread via email attachments or by innocently downloading it off the Internet. It can cause a great deal of harm (particularly if it infects Windows and the like), or just a small amount (small program).Fortunately for computer users, there are anti-virus programs available anywhere, whether in the Internet or at the computer shop. These programs specifically target over thousands of viruses and wipe them clean from your system (if infected) or protect you from incoming attacks (if not yet infected).Anti-virus programs are constantly updated (normally everyday) since there are always new virus definitions each day, and you can get infected by these new viruses. These software developers are always researching about the newest viruses to ensure you, the user, are protected from these viruses as much as possible. Your PC security and safety are always being considered.