Well Henrique - RJ,
That is why we have installed special programs to scan and protect against these spyware infections. Ad-aware, Spybot S&D, Spyware Blaster (install only onto a clean system), Ewido or/and A-square free. All these programs are free and additional to avast or any other resident av-program. Not a single av-program can find all malware that exists, so you always use a multi-layered defense to keep a clean machine. Get accustomed to these routines,
That you will stay secure and surf safely is the wish of,
polonus