Security firm Sophos has published an open letter to Facebook about its security and privacy measures on the popular social networking site, and the message is clear: It's time for some changes in order to better protect users.In its Naked Security blog, Senior Technology Consultant Graham Cluley tells Facebook that protecting users is easily accomplished with three changes. They include:PRIVACY BY DEFAULT"No more sharing of information without your users' express agreement," states Cluley in the post. Users should be able to opt-in to sharing, not the other way around, he said. "Whenever you add a new feature to share additional information about your users, you should not assume that they want this feature turned on."Also see: 10 security reasons to quit Facebook and Social media risks: The basicsVETTED APP DEVELOPERS"It is far too easy to become a developer on Facebook," said Cluley. "With over one million app developers already registered on the Facebook platform, it is hardly surprising that your service is riddled with rogue applications and viral scams. Only vetted and approved third-party developers should be allowed to publish apps on your platform."Cluley and other security and privacy advocates have long criticized Facebook over the lack on controls it has in place for application development. As a result, many applications are actually scams that lure users into traps by promising them a download of 'the dislike button' or by appealing to their vanity and promising them an application that will show them who is viewing their profile. Instead users end up with a survey scam or with a malware download on their computer.HTTPS FOR EVERYTHINGMore about Facebook security and privacy Social media risks: The basics 10 security reasons to quit Facebook 4 tips for Facebook from security and privacy experts 4 reasons why Facebook and vanity don't mix Facebook recently introduced a HTTPS option, a move that was lauded by security professionals. But the feature is turned off by default, noted Cluley, which means many users are not even aware that it is possible to enable it. "Worse, you only commit to provide a secure connection 'whenever possible,'" Cluley said."Facebook should enforce a secure connection all the time, by default. Without this protection, your users are at risk of losing personal information to hackers. "