Faked sender's address

[Note from moderator: Walter is not alone in having this experience, note also that other subject lines are used, caveat lector.] Dear categorist: It seems that a number of categorists recently received a message showing as sender tholen@mathstat.yorku.ca, as subject "Re: application", with an attachment that, of course, one should not open. Let me clarify that I never sent such a message. I have been told that in all likelihood my address was used to disguise the virus-affected machine that sent the message and that was the real target of the attack. Regards, Walter.