Yes, it's true. You may have inadvertently invited a spy into your computer. This spy is known as "spyware, adware, or trojans", and once it is in your computer it starts taking statistical information as you travel Internet. In some cases, it may send you pop-up ads and slow down your computer. A wired.com article, mentions it "could even collect your credit card information".
How did you invite spy?
Maybe you visited a website you knew and enjoyed only to find that it was recently purchased by a pornography site. The new company has imbedded "spyware" into home page and now, in many cases without your knowledge, it is on your computer.
Maybe you downloaded a free or paid program and as part of package you were provided with an added secret bonus – a “spyware” program. Spyware may also be placed on CD’s you purchase, too.
Maybe you agreed to it! You could have downloaded a program and checked box to allow program to take statistics from you "for their own use".
Maybe someone sent you spam, especially porn spam, and that spam created spy. Spys can easily be placed, without your knowledge, in pictures or HTML email.
What you can do?
Purchase a firewall program and it should let you know if a program is about to download from website you are at. Note word "should".
Or you can learn all about spyware, download an anti-spyware program, and schedule time in your weekly calendar to run an anti-spyware program. The first time I conducted a ”clean up”, on my 18-month old computer, I found 2 porn and 42 other spyware programs. Then a week later, I had 4 new spyware files appear.
To further reduce amount of spyware that ends up in your e-mail Inbox, create a "rule" or "filter” that will move any e-mail containing "certain adult words of your choosing” directly to your delete or spam folder.
Norton and MacAfee virus protection specialists, have added anti-spy programs to list of maintenance programs they sell. However, according to information I’ve seen on email lists, they’re not as anywhere as good as Ad-aware program from Lavasoft.