Do you mean can spyware be installed without your knowledge? It's conceivable, but AFAIK there have never been any such cases.
No matter what system you're on, there's always going to be the potential for trojan horses, which are applications that pretend to do something innocent, but really do something nefarious. Like I said, there are no examples of such programs on OS X that I know of, but the potential is, has been, and will always be there.
Just be careful what you download. Sites like macupdate.com and versiontracker.com are your friend: if a program is listed there, it's most likely legit, so don't worry too much.
There has been one case a few years back, at least according to the Italian media.. with some sort of spyware, on Macs. Someone, a single person, was spying one Italian semi-famous person, which was using a Mac. However the news never specified which OS he was using, or any otehr details. I think this happened around 2002.
And that was all of any spyware even remotely on OS X ever. And being in 2002, it is not even sure if it was OS 9 or even pre that, or OS X.
There are plenty of keyloggers for OS X - just search versiontracker for them.
It would be fairly easy to make a program that installed a keylogger if you open it. No OS can protect you from malware if you open attachments indiscriminately. As Gia said, I've not heard of anyone doing this, but it would be quite easy to do for any programmer.
it was my sister , downloading files from habbopro.com , a site which lets you download 3rd party tools for a game called habbohotel,which is a game for kids ,and as im only 15 i dont really have clue ...
My Sis Says People On That Site Advertise Tools For It, She Downloaded Some And They Didnt Work Atall , And As It Is A Site Were You Have A Username And A Password , People Will Want It To Steal Youre " Furni " ( Virtual Furni Which You Buy With " Not " Virtual Money ) , And As I Have Read On A Help Site It Is Common For People To Put Spyware In A Fake Tool Download..