If you are asking about the different categories or titles that viruses fall under, then the number is rather limited. Computer programmers have come up with a few different names for them, but they all basically perform a malicious function of some sort or another. On the other hand, if you are asking how many viruses are on the actual Internet on any given day then the numbers are going to be staggering to say the least. At the low end of the computer virus spectrum there are several thousand active and ready to be downloaded on any given day. Current statistics indicate fluctuations in the amount of viruses created and distributed annually, with some numbers reaching as high as 52,000 for a given calendar year.
What does this mean to us as computer users? Basically that there are roughly 143 new viruses created daily on an annual basis. That number, as well as computer technology and the people that use it will double or even triple in the next decade. This is absolutely mind boggling when you consider that currently only 32% of the world's population accesses the computer on a daily basis
There really isn't any way to determine the exact number of viruses that have been created to date, or how many will crop up in the future. The only thing that seems absolutely certain is that as long as there are computers there will be computer viruses. The problem lies within the technology and computer language used to write programs. It can be used for good intentions or for bad; it just depends on who is using the software to write the program. It stands to reason that as technology continues to advance so will the abilities of hackers and the problem will be with us throughout the rest of humanity.
It would seem that the solution to viruses should be rather simple. All it really involves is the proper education of how Internet technology is used both for good and for bad. Think about it this way, every time something new arrives in the form of technology, such as smartphones and tablets, they present hackers with a new target audience. Same thing with cloud computing, it may not have been affected yet, but it is just a matter of time before somebody invents a virus that can penetrate any of the protective features a cloud has to offer.
It is impossible to accurately identify each and every virus that is currently out there. Unfortunately due to the nature of computer language and how it is used to create malicious computer codes that result in virus definitions, viruses aren't recognized until they have been discovered on an infected computer. Every time computer programmers come up with a new idea to combat virus infection they open up more avenues for virus researchers to explore and exploit.
Smartphones operating on Google's Android operating system launched approximately 4-5 years ago, and in 2011 they became vulnerable to virus infections as did tablets running on similar Google platforms. Cloud computing will undoubtedly follow in the footprints left behind by its predecessors and eventually succumb to computer viruses.
How do you prevent viruses from infecting your computer? You look through several anti-virus reviews and you will notice a common theme, develop good, strong browsing habits. Research and educate yourself as well as others. Use good judgment; stop making the same mistakes over and over. If they didn't work for you the first time and led you to catching a virus on your computer, what makes you think you will have any different results by doing the same things?