The huge cache of personal data comes from a hack of the website four years ago that was previously thought to have affected only a few million accounts.

LinkedIn said it was trying to assess which accounts had been affected and invalidate their passwords to prevent hackers accessing users accounts.

Although encrypted, the set of passwords had not been cryptographically-sealed with an additional security measure known as a salt , making more common passwords relatively easy to decode.

The data release actually contains 167 million account details including email addresses, although only 117 million passwords are included.

It said that passwords are now salted, meaning in the event of any future breach, they would be less difficult to crack.

One ultra-secure one won't be any good if someone finds it

While combining upper and lower case passwords with numbers to alter a memorable word - M4raD0na - is often advised, these are more easily cracked than you might think

Good advice is to make a memorable, unusal sentence: "I am a 7-foot tall metal giant" is better than "My name is John", and use the first letter of each word with punctuation: "Iaa7-ftmg"

Alternatively, you can use a password manager such as 1Password, which can generate secure passwords and store them online

The best way to protect yourself is to use two-factor authentication, which will send a text with a code or use an app to verify your log-in

If your LinkedIn password has not been changed since 2012, now is probably a good time, and the same goes for any other websites which you use the same password for.

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