Dangerous "billing", "invoice", "receipt" emails

This morning a dangerous email started showing up on campus with a subject line of “billing”, “invoice” or “receipt”.  The email has a .zip file attachment with a virus-downloader inside.

IF YOU RECEIVED ONE OF THESE EMAILS PLEASE DELETE IT.
We believe this to be a “ransomware” virus which encrypts data and files on a computer or a network share so that they are unreadable.  A ransom is then demanded in order to unlock the files.  Sounds unbelievable but this type of attack is effective and many companies and organizations do indeed pay the ransom.
If you did open the .zip file let me know immediately.  This type of virus is particularly dangerous and can be very expensive and time consuming to recover from.
If you have ANY doubt about the legitimacy of an email, forward it to spam@williams.edu before you open the attachment.  The sooner we know about these threats the more likely we can prevent a major event.