After a period of relative quiet in the area, Apple has debuted four new Get a Mac ads, claiming the superiority of Macs over PCs. In the first, "Biohazard Suit," PC is dressed in protective garb because of a "major new PC virus" circulating the Internet. As many as 20,000 new viruses or pieces of malware appear for PCs each day, the ad alleges. The first Mac botnet recently became active.