Until now, how people choose their computer passwords has been a mystery. But domain names seller CentralNic has found the selection process may not be very complicated and may not be at all safe.

CentralNic polled 1,200 internet subscribers and found their passwords fell into four distinct categories: family, celebrities and sports stars, fantasy and cryptic.

Almost half the users polled chose passwords associated with their family. Of these, children's names accounted for 20.5 percent, pets' names six percent and dates of birth 2.6 percent. But, worryingly, 55.3 percent of those using a ‘family’ association, chose their own name as the access code for their PCs.

These users “appear to be people who are not computer-literate but have incorporated computer use into their everyday life and choose passwords which symbolise people or events which have emotional value to them," said Prof Helen Petrie, a specialist in human-computer interaction and the psychology of new technology.

David Beckham, Michael Owen and Ryan Giggs were the three most popular choices of password among sports fans, while Robbie Williams was top of the pops with music lovers. Celebrities’ names accounted for almost a third (32 percent) of passwords chosen.

"So many people tend to subconsciously believe their password has to sum up the very essence of their being in one word," said Stephen Dyer, chairman of CentralNic. "This makes it potentially very simple indeed for anyone to access their computer or secure internet sites."

The study found the cryptics (11 percent of poll respondents) had chosen the safest names since their passwords had no personal meaning to the individual.

"Although it may be more fun to have Homer Simpson as your log-on, it would be much safer to combine letters and numbers to create a unique, secure password," said Dyer.

Some of the more unusual login names revealed were Delia Smith, Anne Widdecombe, goddess, slapper and Bitch. There's no accounting for taste.