I don't know, Dan. I know it's sent out via email, but DH says that if it's on your machine (through email), it can be *run* from an external page.
All I *know* is that I did *not* run any of the 90-some-odd attachments I've gotten in the last 2 days, and I still got the virus. 3 variations (D, E, and F) on my machine. (I also know DH didn't run them, and neither did Skye or Sienna.

)
All I *know* is I had Norton on my machine, running, updating, scanning email, and *still* had 88 instances of SoBig get through its protection.
All I *know* is now that DH has cleaned the machine and replaced Norton with McAfee, the 3 *more* messages I just got with yet *more* copies of SoBig on them were all caught and removed *before* getting somewhere that I *could* run them.
Alex -- it may be slower, but of the 2 versions readily available to us (McAffee and Norton Corporate, both through work, one through my work one through DH's), McAffee has done one heckuva better job keeping my system clean than Norton. DH says it's because the *version* of Norton I have apparently doesn't interface well with Eudora, the mail program I use primarily. I'd rather have a slower virus program that actually *catches* the virus rather than a faster one that lets 88 instances through.