This is a worm that autoexecutes itself when the message is opened.
It works on _JavaScript and will resend to everyone in your address
book! The worm apparently only works through the yahoo.com and
groups.yahoo.com messaging systems.
Please read more in depth at the following link:
<http://securityresponse.symantec.com/avcenter/venc/data/js.yamanner@
m.html>