Blocking mail with a .gif attachment

Rather than wasting your time setting up custom rules for those cases, I advise you to just mark them as junk.

I did understand you, but it seems you didn’t understand me.

How does one mark an email based on an attachment?

Just like you would do with any other message, i.e. click the Junk button in the toolbar, or do Message > Mark > As Junk Mail.

nowhere do I see a way to base a rule on attachment naming.

In Mail 2.x, Any Attachment Name is one of the available conditions when setting up a rule. I don’t know whether that condition is also available in Mail 1.x.

What I’m suggesting you to do is manually marking as junk any messages the junk filter doesn’t catch, attachments or not, instead of setting up rules for them.

what is the advantage of that over simply deleting the junk upon arrival?

That the junk filter “learns” and would end up automatically recognizing most of those messages as junk.

Not specifically for gif attachments, but these articles provide some good tips for stopping the latest image spam:

<http://www.hawkwings.net/2006/11/27/image-spam-powered-by-russian-bot-net>
<http://www.hawkwings.net/2006/08/01/mailapp-rule-fix-for-image-spam/>
<http://www.davids-world.com/archives/2006/11/the spamavalan.html>

Cheers Martin