When your computer become sluggish and less responsive than several days ago and you didn’t installed new software, you better monitor your computer deeper. Perhaps there is an unwanted Spyware installed without you’ve ever noticed.
Spyware is, simply enough, software that spies on you. It can be installed automatically as part of other software packages (often with ‘free’ smileys or toolbar software), or can be installed simply by browsing on a malicious webpage.
The effects of spyware can vary. Some forms of spyware simply keep a log of your browsing habits, and send reports to databases elsewhere in the world. Some nastier forms of spyware actually search through your hard drive in order to find personal information and credit card numbers.
The same thing could happened with you PC when your computer infected with adware.
Adware is related to spyware, in that they’re both obtrusive and irritating forms of software that usually get installed without the user’s consent. What adware does, though, is plaster your computer screen with ads.
As you can imagine, there’s a lot of money behind this. There are many unscrupulous companies paying either desperate or unscrupulous programmers, and this leads to a lot of headaches for anyone who owns a computer.