Malware-fearing Mac users have been able to breathe easier since Apple released Security Update 2011-003 earlier this week. The key elements of the Security Update were that it successfully detected and removed a couple variants of the Mac Defender Trojan horse, and also added a daily check for new malware definitions.
Not even 24 hours later, some malicious folks released a new version of the Mac Defender Trojan horse into the wild--a variant that Apple's initial update couldn't detect. The antivirus folk refer to the new incarnation as the "C" variant.
If you haven't yet installed that Security Update and do so now, you'll automatically get Apple's up-to-date security definitions, which include the new C variant of Mac Defender. But if you--like me--installed the update back on May 31 then your definitions might still be out of date.
Even if you leave the new Security preference to "Automatically update safe downloads list" checked, your Mac might not have run that check itself yet. And if you--again, like me--would prefer that your Mac go grab the latest definitions right this second, it can be done.
First, check to see whether you're already up to date or not. Launch Terminal, and paste this command:
What do you see? At this writing, some folks (with the old definitions) will see (among some other data) a "last modification date" listed as Thu, 26 May 2011 02:24:41. (If you see any later date, you're more current than this tutorial, but the instructions below will still help ensure that you have the latest malware definitions.)
Now, to force your Mac to update, follow these steps:
1. Launch System Preferences
2. Go to the Security preference pane
3. Uncheck the "Automatically update safe downloads list" box
4. Re-check that box.
Ta-da! Now, if all goes well, and you re-run that Terminal command from above, you'll see that the timestamp has changed. As of this writing, the "last modification date" should be Wed, 01 Jun 2011 21:19:15 GMT.
You needn't run this command every day; your Mac should automatically update that list as long as you leave the checkbox checked. But if you want to make sure you're current because you've heard about new, unpleasant malware on the loose that might harm your Mac, now you know how to force an update.