Hackers yesterday shut down one of the most popular porn sites on the internet.

Redtube.com is in the top 100 most visited websites, and was temporarily shut down by a 'Turkish cyber-terrorist' group calling itself 'Hacked Netdevilz'.

"No porn!" the site read. "We're not the first but we're the best."

The site, which attracted four million visitors last month, is now back up and running on a different server, but experts are poring over the site's logs to find the vulnerability that allowed the security features to be bypassed.

Redtube posts submitted videos, in the same way as YouTube, and attempts are now underway to discover whether the security hole is common to other web 2.0 sites.