Sounds more like a hotlinking problem than a naming issue.

A good host should be able to block hotlinking - so the spammers will either download the logo ... or go elsewhere.

I'm not clear how naming matters ... you could call it fikughiuhvkvuhth.jpg, and they could still absolute link to it.

Or am I missing something?

It was the name of the file along with the fact that it was a Wells Fargo phishing attempt via email. The client ended up on the spam list due to this phishing attempt and the link. In reviewing the message that was generated from SpamCop, that name wells-fargo in the file is what flagged it.

Long story short? Someone attempted an email phishing exploit. They linked directly to an image on our server that contained the wells-fargo name. Whether you prevent hotlinking or not, this is something that could have an impact. It did for this particular client as their emails starting bouncing as undeliverable due to blacklist issues.

Sorry, but it seems to me far more likely that it was the URL that caused the problems - not the file name.

And preventing hotlinking would (usually) prevent your URL being included in a spam.

I say 'usually', because many spammers are stupid, and don't test before sending; I've received a few with broken images, which may well be failed hotlinking (or the spammer forgot to upload his own!).

It never fails to amuse me that phishers attacking paypal and ebay clients ALMOST ALWAYS hotlink to 'official' images. And they say they care ;)

There is, of course, no way to stop a spammer including your url in their spam, whatever names you give your files.