These programs are generally destructive and are hidden inside e-mail attachments, games, utilities, or any executable application. When run, a Trojan horse tries to do something harmful to your computer under the pretense of being useful. Thousands of hacking programs are available on the Internet. Back Orifice is simply the most famous, Maguire says. It's difficult to estimate how much damage hackers actually do.
Some experts suggest it is overstated by a computer industry eager to sell safety services.
Also, experts estimate 80 percent of hacking comes from within a corporation rather than from outside attacks. The upside of the teeming thousands of amateur hackers is that their prodigious efforts to hack into sites have forced software companies to provide security plugs and repairs to targeted software flaws, Cohen says.