A computer science professor believes that the best passwords are the ones you can't remember.
Professor Alan Woodward, from the University of Surrey, told the BBC that making a mistake typing an email address could be like "handing over the keys to your digital life" as valuable data is being put at risk.
Expanding on this, he also said the same was true for passwords, where overly complex combinations often led to errors as people try to create strong passwords to thwart hackers.
"There is plenty of evidence now to show that using any form of a proper word, be it transliterated by replacing 1 with l or 0 with o or whatever it happens to be is subject to cracking simply because so many guesses can be made per second with modern based systems," he told IT Pro.
"And even making your phrase longer doesn't help - there's actually some evidence to suggest that longer phrases make it easier to crack. Hence, a truly random collection of characters is best and you'll never remember those if you have as many accounts as I do, so you have to use a password manager."
An example of incorrectly inputting an email address allowed the BBC to see details of a stranger's credit report. Personal details listed on credit scoring site ClearScore were seen by someone with the same name. One person applied to sign up to the credit service but made a small error entering in their email address, which often doubles as the username.
The slightly incorrect email address actually belonged to someone else, who received an email allowing them to access the account, change details and see a range of personal information, such as date of birth, previous address and historical banking details like credit cards, loans and payments.
After being alerted to the case, a ClearScore spokesman said to the BBC: "When something like this happens, ClearScore makes the worst-case assumption that it is fraud and locks everything down."
The website has a reminder at the sign-up stage urging the applicant to ensure the correct email address is used. There is also information on the site about staying safe from fraud.
Making sure your passwords are strong enough can often be a problem, with people making them either too complex or not unique enough. For Professor Woodward, the best passwords are ones even you can't work out.
"Personally, I think the main issue with passwords is that the best password is the one you can't remember," he added. "In fact, if you tried to beat any of my passwords out of me I couldn't tell you - I do as I recommend and have a password manager. That way I have to remember only one strong password to access the others.
"Using password managers is one of the reasons I implore site operators to allow cut and paste of passwords - making someone manually transcribe a password from a password manager to a site login screen is tedious and adds no security. The more difficult you make it too have strong access control the more likely users will find ways to work around it and essentially circumvent all your lovely strong password protection - we've all seen the sticky notes stuck to screens with the 'strong' password."
