Now this: Mac malware is now circulating across the Net via pirated copies of Apple’s new iWorks software.

The “iServices.a” Trojan hitchhikes on iWork ’09′s installer. The installer for the Trojan horse is launched as soon as a user begins the installation of iWork, following the installer’s request of an administrator password.

Once the Mac is infected, the Trojan phones home to let daddy know it arrived safely and is awaiting further instructions. Since then, the same bit of viral nastiness — dubbed OSX.Trojan.iServices.B — has begun showing up in pirated copies of Adobe Photoshop CS4, according to Macworld.

Glass-half-full types can view this as further proof of the Mac’s success; it’s now installed in sufficient numbers to be worth the attention of botnet herders. Also: That room full of manure is sure to have a pony inside.

Web sites saw visitors deserting Microsoft’s Internet Explorer browser in favor of Apple’s Safari, Mozilla’s Firefox and Google’s Chrome in December, according to Web analytics company Net Applications.Internet Explorer was used by 68.15 percent of Web surfers monitored in December, down from 69.77 percent in November and 71.27 percent in October, according to preliminary figures published by Net Applications on its Hitslink Web site Friday. IE’s share has slipped from around 75 percent since the start of 2008.

Safari, Firefox and Chrome all profited from the slide in IE’s popularity.

Firefox’s share rose to 21.34 percent, from 20.78 percent in November and 19.97 percent in October, while Safari’s climbed to 7.93 percent, from 7.13 percent in November and 6.57 percent in October.

Google’s Chrome browser topped the 1 percent mark in Net Applications’ survey for the first time, with a share of 1.04 percent, up from 0.83 percent in November and 0.74 percent in October.

Opera’s share remained steady at 0.71 percent.

Net Applications warned that decreased workplace use of the Internet in December may have biased its results.