Undoubtedly one of the worst things that it could happen to a computer user is to be attacked by an unknown computer virus. Knowing how to react in such cases it's really important so that the possible loss of information could be minimal.
Above all, we must distinguish two types of “victims”: the home users, with only one computer in their home and the system administrators of a network with several or hundreds of machines. In each case you must act quickly, but without being panicked.
If you are a home user, you must distinguish two phases: first, the presence of a dormant virus and on the other hand, the payload. It seems logical that the effects will be visible and the user can quite easily detect that this is a virus: messages on the screen, graphic effects or, at worst, loss of data are common effects of the virus.
Recognizing a virus during the phase that it lies dormant, stealthily infecting our system, it is no doubt the best thing we can do, because in this way we can avoid unpleasant surprises. One factor that may reveal the presence of viruses are increasing the size of the files, a sign that may have been infected by a virus attached to them.
Other side effects of the virus, such as blocking system errors when running programs, reduction of the hard disk space or memory, is considered almost indisputable evidence for the presence of virus in MS-DOS systems.
If the effect has not attacked our files directly, or whether the loss was partial, we collect samples of any infected files. Remember that in most cases, may be executable files or documents, not to mention other types of viruses such as boot, though with the entry of Windows have been diminished.
Unfortunately, it may be that the virus has destroyed all the information on your hard drive. In this case, we must turn to discs that we have recently used, where we should look for a document or executable that could have been infected.