Is there a botnet using Macintosh machines? yes, it seems so.
http://arstechnica.com/apple/news/2009/04/...t-is-active.ars
Is it new. No not necessarily.
http://voices.washingtonpost.com/securityf...rss=securityfix

Are all/most Mac machines vulnerable. I does not seem so.
Only those owners who downloaded a pirated version of iWork or Photoshop CS4 are currently involved.

Macintosh still enjoys "security through obscurity", at least to the limited extent that Macs still only hold about 10% of market share.
So they are not thought to be an economically viable target... yet.

But if a Mac user is running MS applications and/or Windows, and/or does file sharing, then those softwares are vulnerable and the Mac user's machine may become a vector for spreading infected files to their address booked correspondents.

What's to be done?

• keep your Mac OS updated. yes update it.
• Avoid falling for phishing schemes and refuse to download/install pirated software.
• Even running FireFox as the default browser may be an added benefit over Safari

Do you need an Antivirus. Probably. but more in respect to your correspondents than your Mac system at least for now
There are commercially available AntiVirus products.

• ClamXav remains a free option ClamXav,
• Norton has a product for Macs & PC's
• Intego offers VirusBarrier
• PC Tools offers a free and paid version of iAntiVirus

Question:

What other security utilities do you Mac owners use?