A quarter of Facebook  users have a least one friend who's accidentally spreading malicious content via their profile, says BitDefender.

The security firm monitored users of its Safego for Facebook application, which scans profiles for mal;icious content and revealed 25 percent of users had at least one friend who had shared infected content, such as links or video clips, on their profile.

However, only 0.7 percent of Safego users had spread malicious content to their friends.

"These statistics reinforce the fact that everyone should exercise caution when using social networks - for their friend's sake as well as their own. Simply trusting that people won't post malicious content is not enough, as in many cases they may do so without realising due to the application posting on the user's behalf," said Catalin Cosoi, Head of the BitDefender Online Threat Labs.

BitDefender revealed the research as it launched the full version of its Safego for Facebook app. The app scans the newsfeeds of users and flags up any malicious content, as well featuring an integrated quickscan that will check a PC for threats within 60 seconds.

The app can be downloaded now for free from BitDefender's dedicated Facebook page.