Naoki Hiroshima, a software developer from California, has had the Twitter handle @N since 2007.
Mr Hiroshima said that a hacker gained access to his GoDaddy account - a domain name registration service -
and had changed the account settings to gain access to his personal email. In a subsequent email exchange, the hacker told Mr Hiroshima that he had managed to access his GoDaddy account
by learning the last 4 digits of his credit card number.