Nearly one-quarter of Britain's 50m mobile devices are not password-protected, according to a study.
A total of 73% of 2,033 mobile device users surveyed by Experian CreditExpert professed to be tech literate, yet only 37% were found to have a password or pin on all their devices, and 27% on some.
Of those without any password security, 43% shared their device with family, friends or colleagues.
And just 17% of mobile device users accepted security updates, such as OS upgrades, meaning their personal information could be left at risk if their device became compromised.
The research, which was conducted to mark the beginning of National Identity Fraud Prevention Month, discovered that a third of those surveyed cite social networking activities as their biggest fear as a way for people to steal their personal data - though many users also admitted to revealing personal information through such sites which could be used to commit identity fraud.
Six per cent of people check-in to locations via Facebook, meaning people know their house could be empty, while 22% of 25-35-year-olds and 29% of 16-24-year-olds accept friend requests from someone they do not know.