From the ZD Net website there was an article or blog about Virus now attacking Mac computers. They recommend downloading an anti-virus program called "Sophos Anti-Virus Home Edition". It is a free program for Macs.
Does anyone have an experience with that program or know anything about its merits or effectiveness?

It's not a virus. It's a trojan and you must give it your permission to install itself. Most anti-virals cause more headaches than they cure. I don't run any of them. I do use normal caution and don't download from unknown sites. I don't automatically grant permission or put in my password unless I'm trying to deliberately install something. My browsers are set to download only to the desktop (where I can see what's going on) and to not automatically expand archives. Common sense will keep you safe.