In the beginning spam was just text. – Spam filters adapted to block that.

Then spammers started to use html. – Spam filters adapted to block that.

Then spammers started to use images. – Spam filters adapted to block that.

Then spammers started to use PDF attachments. – Spam filters are adapting for that right now.

And now spammers are starting to use Office files…

Like this case in point. Let's say you receive an e-mail with just a zip. No subject field, no text content:



The ZIP contains a single Excel spreadsheet file:



…and when opened in Excel… it's just stock spam.



Such spam gets through filters better… and people probably pay more attention to them, too.

Of course, opening unknown XLS files is always risky as there might be malicious code embedded. However, in this case it was just spam.

What next? Attached MP3 files that are radio commercials? Haven't seen that yet but I'm sure somebody's already tried it.