It pretends to come from the Better Business Bureaus containing a message something like this...
Subject: BBB assistance Re: Case # 41943714
The Better Business Bureau has been sent the above-referenced complaint from one of your customers on the subject of their dealings with you.
The details of the consumer's concern are explained in enclosed file.
Please review this issue and let us know about your opinion.
We kindly ask you to open the ATTACHED REPORT to reply this complaint.
We look forward to your prompt attention to this matter.
Better Business Bureau
Attached is a .zip file The attachment contains a particularly nasty virus