Companies are having their security put at risk by employees writing down or sharing their passwords according to a new survey.

The study by encryption and secure access company SafeNet of 67,000 people found that 50 percent of respondents still wrote down their computer passwords. Over a third shared their passwords with other users.

But companies themselves were taking security more seriously by implementing policies requiring longer passwords or ones containing alphanumeric characters. However, this has bought its own problems as these more complex password were difficult to remember and users had to change them more often. 30 per cent of respondents were required to change passwords seven or more times in a single year. This figure had risen three per cent from last year's survey.

The survey found that the number and complexity of passwords increased the likelihood of users forgetting or writing down passwords sharply.

"This survey reinforces what we hear from our customers about their information security concerns," said SafeNet chairman and CEO, Tony Caputo. "Whether employees are writing their passwords down, or frequently calling the internal help desk because they can't remember them, the organisation can be at risk while experiencing loss of productivity."

The survey questioned a mix of customers, prospects, partners and resellers of SafeNet in the US, UK, France and Germany.