Security experts Sophos say a dozing bank clerk who "nodded off at his keyboard during a transaction" has taught us all a security lesson.

According to a recent story in The London Evening Standard, a payment of 64.20 euros instead came through at a whopping 22,222,222.22 euros due to a case of sleepiness on the job.

The newspaper reported that: "The clerk was making a payment of 64.20 euros (£54.60) but as he fell asleep he left his finger on the number two key, accidentally putting through a payment of 22,222,222.22 euros (£189,682,360)."

After being missed by the clerk's supervisor, a fellow colleague picked up on the gaffe before it was too late, but Sophos' Paul Ducklin believes we can all learn from such errors.

"We know that there are some tasks that we simply oughtn't to attempt when our judgements are impaired, say through tiredness or alcohol," he wrote.

"Yet many of us insist on living our digital lives logged in semi-permanently to sites such as Facebook, Twitter, webmail and more, thus actively and unashamedly inviting upon ourselves exactly this sort of 22-million-Euro-blunder moment.

"It's not just that we're more likely to initiate an unwanted bank transaction (or send an unintentionally ruinous email) while we're tired or lit.

"It's that by leaving ourselves logged in unnecessarily, we make it easier for our computer to do just such a thing if it becomes impaired, for example through misconfiguration or malware infection."

Emphasising the need to log-out and refrained from staying logged into every available website going, Dulkin suggests users should entertain a change of approach online.

"If you are the sort of user who likes to log in and stay logged in, especially to on-line services, why not give yourself a week's trial of logging out whenever you can, especially from on-line services?

"Try it: you may thank yourself one day."

To read Paul Daulkin's full blog, click here

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