varjak paw wrote:
As to your system, again, there have never been any viruses or worms on Mac OS X, and only a few trojans, most of which Apple blocks from installing in Mac OS X 10.6 and later. So I definitely do not recommend installing Norton or any of the other commercial antivirus applications...
Flashback has evolved beyond the simple trojan stage into "drive by" malware that doesn't require a user to do anything besides visit an infected site. (The Java vulnerability that makes this possible has been patched in recent security updates, but it is no longer strictly true that only trojans exist in the wild for OS X.)
Plus, since this Mac is being used to upload files to a web site, it is worth considering using AV software on it to detect & remove Windows malware that might be uploaded to the site, triggering a warning like above for users that visit it.
Norton doesn't have a good track record with OS X but a few other commercial AV apps are worth considering. I use Sophos Home Edition for Macs & have had no problems with it.
See Mac Malware Guide : Do I need anti-virus software? for an overview of the subject.