Tab napping is more sophisticated than phishing scams and it doesn’t rely on persuading you to click on a link to a scammers Web page. Instead it targets internet users who open lots of tabs on their browser at the same time. How does it work? By replacing an inactive browser tab with a fake page set up specifically to obtain your personal data - without you even realizing it has happened.

So, don't assume that after you have opened a new tab and visited a Web page, that Web page will stay the same even if you don’t return to it for a time while you use other windows and tabs. Malicious code can replace the Web page you opened with a fake version which looks virtually identical to the legitimate page you originally visited.

You can guard against tab napping by keeping a close eye on tabs you open. Make sure the URL in the browser address page is correct before you enter any login details. A fake tabbed page will have a different URL to the Web site you think you’re using. Always check that the URL has a secure https:// address even if you don’t have tabs open on the browser.

Read more: http://www.lovemoney.com/news/get-the-best-deal/scams/the-new-scam-that-secretly-steals-your-bank-details-4993.aspx