Berlin  - Firefox users should carefully review any security warnings they receive from their browsers. That's because such warnings are not always indicators of a real threat, says Germany-based antivirus firm Gdata.

The impetus behind the fake messages is profit, not security. Hackers are currently attempting to use so-called trojans to trigger fake security warnings in Firefox, Gdata says. The software then redirects the user to a different website where they are encouraged to buy "counterfeit" antivirus software that pretends to find an infection on the computer.

No matter what the site claims to find, users shouldn't be tempted to download the "scareware." The best thing to do instead is to update a reputable virus scanner and re-scan the computer.

Hackers have also come up with a way of preventing users from realising they're being redirected. They do so by ignoring the user's individual computer and instead going after DNS servers on the internet. DNS servers are part of the infrastructure of the internet, converting website names into versions that machines can read.

Hackers can sometimes manipulate the servers to send browsers to the website of the hacker's choice, even if the correct website URL is entered into the browser. Therefore it's a good idea to keep an eye on the browser's address bar. It shows what page the surfer has really visited. (dpa)