To complete 'dual authentication' I have received messages several times which Norton Ask Genie suggests to be suspicious, from an unrecognised number, with an unusual format for an authentication code and goes on to suggest it could be an attempt at phishing to attempt to steal personal information. They arrive during the delay experienced to received the expected format of message attributed to Yahoo. I have now learn to ignore these malicious messages and to request another message which then proves to be the correctly formatted one. One malicious message reads: "+1 213-502-9720" in the title followed by "Exp. soon : 506 316". It attempts to imitate a message for a dual authentication code. Strongly, I suggest there is a problem with the technology used to communicate the codes for dual authentication. I log on to my account with Yahoo with the email address with a @yahoo.co.uk. I suggest this is a fundamentally important security problem that Yahoo need to rectify.