How do you know if your computer has a virus, a worm, a trojan
horse infection, spyware, malware, crimeware or any of the other known
types of infection? Obviously, everyone's PC is different, so it is up
to each person to keep an eye on the known and documented causes.
Although
not all of the following symptoms will necessarily indicate your PC has
an infection, if you note more than just one of them happening at the
same time, there is a high probability and you would be advised to look
into it further.
1. Performance is sluggish now compared to what
it was when the computer was new. Unfortunately, there is no single
cause; it is likely to be any of the following or a combination of them:
virus, worm, spyware, Adware, rootkit (provides remote access to a PC
without the user's knowledge).
2. PC taking longer to boot up.
This happens anyway as you load more and more programs, especially if
your computer is older and you're trying to run the latest resource
hungry applications, but it's worth checking for malware or other
infection that has been added to the start-up sequence.