W32/Frethem

W32/Frethem is a worm, which arrives as an infected email attachment. W32/Frethem uses a MIME header vulnerability and an IFRAME vulnerability so that the attached file is run automatically when the email is viewed on unpatched Microsoft email clients. W32/Frethem may cause denial-of-service conditions in networks where multiple systems are infected, or large volumes of infected mail are received.