Spammers targeting Xtra today?

Seems like addresses pretending to be my net provider Xtra.co.nz are being used by spammers. I've had 4 messages today with dubious .zip file attachments supposedly from Xtra. All deleted thanks to Mailwasher.

UPDATE: Have had bogus emails over the past few days from info @ xtra.co.nz, register @ xtra.co.nz, admin @ xtra.co.nz which were all carrying .zip files. Strangely these got past the Xtra spam filter which I have activated. I downloaded one to see if a virus and Norton detected it was infected with the W32.Mytob.CU @ mm virus. The rest I zapped with Mailwasher before downloading.