The personal details of millions of job seekers have been stolen in the largest data theft in Britain, The Times has learned.

Hackers gained access to confidential details provided by 4.5 million people to Monster.co.uk, the online recruitment site.

Names, passwords, telephone numbers, e-mail addresses, birth dates, sex and ethnicity data as well as other "demographic information," were all stolen, the company admitted Monday.

It is the most extensive breach of confidential data since the British tax and customs authority lost the details of 25 million child-benefit recipients in 2007.

The victims are mainly professional staff who are seeking work in the economic downturn. Registrations at the site, which allows employers to browse thousands of resumes online, have soared as layoffs have risen.

"It's a horrendous breach," said Graham Cluley, of Sophos, an IT security firm. "The information they have can be used to cause all kinds of mischief."

• Click here to read the rest of this article in the Times of London.

• Click here to visit FOXNews.com's Cybersecurity Center.

• Got tech questions? Ask our experts at FoxNews.com's Tech Q&A.