Telephone numbers are simply and clearly the basis for user names, and WhatsApp passwords - at least on Android phones - are clearly based on a phone’s IMEI serial number. This is because WhatsApp is set up to make the service friendly to new users who don’t have to provide their own combination of user name and password – they just use the existing info relating to their phone as login data. In his blog British web developer Sam Granger writes that any relatively ambitious hacker could get into WhatsApp accounts without a problem, either to intercept messages or send messages from their victim’s account. However the service, which is run by small San Francisco start-up WhatsApp Inc., is neither as secure nor as failure-resistant as one would expect from a market leader. According to WhatsApp developers, their servers handle over 10 billion messages per day. To the annoyance of cell phone providers, WhatsApp has become a kind of quasi replacement for the old fee-based SMS. It is a favorite application for both iPhone and Android users.

For months, free smartphone instant messaging service WhatsApp has been topping the download charts.

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