"Our engineers found a spam sample that mentions Facebook’s purchase of WhatsApp, and also says that a version of WhatsApp is now available for users on Windows and Mac PCs," explains TrendLabs anti-spam research engineer Michael Casayuran. "The message also provides a download link to this version, which is detected as TROJ_BANLOAD.YZV, which is commonly used to download banking malware."
And that's the case with this campaign -- the malware gathers user names and passwords stored on the infected system with the aim of targeting online bank accounts. "The use of BANKER malware, coupled with a Portuguese message, indicates that the intended targets are users in Brazil," Casayuran notes.
As Casayuran notes, there's currently no Windows or Mac client available for WhatsApp, so any messages offering such a client should be considered scams.