The History of Attachment Security in Outlook, Part 1
http://blogs.technet.com/kclemson/archive/2004/08/16/215499.aspx

Lemson, K.C.
KC on Exchange and Outlook
2008

Abstract:

A partial history of why Outlook has so, so many viruses communicated using it, and how people at Microsoft thought to try and stop it. A study of why minor patches can't repair major architecture issues.