Around 23.2 million hacking victims used '123456' as a password, according to the UK's National Cyber Security Centre (NCSC).
In a list of the most hacked passwords released in collaboration with Troy Hunt, 123456 was followed by '123456789', 'qwerty', 'password', and '111111'.
In a survey conducted by the NCSC, only 15 percent respondents say they know a great deal about how to protect themselves online.
The lack of awareness is particularly prominent amongst older people, the survey said