A wave of fake Twitter email invitations sent in hopes of luring people to unzip a file to find out who invited them has been hitting unsuspecting victims. The message appears as if it came from a Twitter account, but unlike a legitimate Twitter message, there is no invitation URL in the body of the email. Instead, the user sees an attachment that appears as a.zip file containing an invitation card. When the zip file is opened, the virus spreads. It looks around on infected computers and sends emails to addresses it finds.
Source: https://threatpost.com/fake-twitter-invites-spread-worm-062209/72844/