A Web security company is offering a free tool designed to prevent users of social networks from posting embarrassing drunken messages online.

On the premise that "Nothing good happens after 1:00 am," the tool from Colorado-based Webroot promises to "put an end to the embarrassment that follows regrettable, late-night posts."

The "Social Media Sobriety Test" is a free plug-in for Firefox Web browsers.

It requires a user of Facebook, Myspace, Twitter, Flickr, YouTube or Tumblr to perform a coordination test before being allowed to access the service.

The tests include keeping a cursor inside a moving circle or correctly identifying a series of flashing lights.

If a user fails they will be blocked from using a service.

Sobriety Test users can set the hours they would like the blocking tool to be in force.

Google also offers a tool for its Gmail service designed to prevent users from sending drunken emails. "Mail Goggles" forces users to solve five simple math problems in less than a minute in order to send a Gmail missive.