New research indicates that choosing 4-digit pins from birth dates, a year in the 1900s, or an obvious numerical sequence, makes it easy for a thief to crack the password.
Researchers at the data analysis firm Data Genetics have found that the three most popular combinations, "1234," "1111," and "0000", account for close to 20 per cent of all four-digit passwords.
According to The Age, every four-digit combination that starts with "19" ranks above the 80th percentile in popularity.
Also quite common, in the US at least, are MM/DD combinations, those in which the first two digits are between "01" and "12" and the last two are between "01" and "31", the study said.
Therfore researchers say that choosing your birthday, your birth year, or a number that might be a lot of other people's birthday or birth year makes your password significantly easier to guess.
On the other end of the scale, the least popular combination, 8068, appears less than 0.001 per cent of the time, the paper said.
Rounding out the bottom five are "8093", "9629", "6835", and "7637", which are all nearly as rare, the study concluded.