It's not a new technique for fooling people into opening a malicious attachment, but clearly the hackers still think it has some legs.
We've seen a lot of emails in our spamtraps today pretending to be a failed delivery report from UPS. The emails claim that UPS did not manage to deliver a package that you sent on February 23rd, because an incorrect destination address was specified.
All you have to do, says the dangerous email with the subject line "Delivery problems", is open the attached invoice and contact your local UPS office.
Of course these emails aren't from UPS at all, and opening the attached file (Invoice_8612112.zip) is not a good idea at all, as it contains the Troj/Inject-FA Trojan horse.