The earliest worms and viruses were created for geeky fun and did little harm, but how times have changed. There have always been viruses, and as we connect more and more devices, the risk of infection multiplies. In fact there are hundreds of thousands of documented viruses, with more being discovered every day. Some can cause irreparable damage such as data loss, or a serious loss of productivity. Others turn out to simply be a nuisance by causing odd behavior on a system. Some can wipe out the information on a hard drive, tie up traffic on a computer network for hours, or turn an innocent machine into a zombie. Computer viruses can be a nightmare.