I've got spyware!!??

[Joseph Vella]

I just installed flash in Firefox.  I was playing around with the 
autoscrolling feature, when all of a sudden some ugly website pops up.  It 
was something I clicked with the mouse wheel.  I tried it again and sure 
enough the same site pops up.  It was kind of tricky to do. I had to be 
scrolling and then click real fast.  I found that if I turned off the 
autoscrolling, anytime I clicked in the browser window with the mouse wheel 
this site would come up.  On a couple of occasions a page within the 
Microsoft site would come up instead.

I deleted the mozilla directory in my home directory.  After that the first 
three clicks of my mouse wheel would cause the Microsoft page to come up, 
after that the other site would come up.

How could there be spyware on my FreeBSD computer and how do I get rid of it?