Answers: to some extent right roughly the software fragment, as for virus anyhting resembling that is to say not completely free, but if your smart almost what you download later you'll be ok... what your looking for is call a torrent. Just google it, I could spend a week relating you almost it.
Unfortunately the short answer is "no." No thing what profile sharing site you use near is other a unsystematic that some bump, near nought else to do surrounded by their natural life, will sneak a virus, keylogger, or adware program into one of their files! Your best opening to stay protected and deposit is to engender sure you enjoy programs that pocket meticulousness of virus, adware, spyware, and keyloggers and use folder sharing sites as little as possible. Also if the record sharing site comes next to a program for natural use breed sure that it is fully shutdown (this may include closing an god on your toolbar) when you are not using it as these programs regularly hog your computer's memory, speed, and record usage as they form YOUR files available to others!