There are a lot of different worms and viruses out there. You may think that the entire thing is beyond your control. However, it really is no more beyond your control than a biological virus. A biological virus, when it infects the host, becomes apparent by way of certain observable symptoms. You are not going to get a little notification on your screen saying “You are infected with the BLAH virus”. Instead, you will begin to notice things that are out of the ordinary.
Here are some typical signs that your computer may be infected with a computer virus:

Please