Twitter's Vine, a new video app for Apple devices, now warns users that it "contains age-restricted material" and that no one under 17 is allowed to access the app. The warning came in response to a proliferation of pornographic content since Twitter rolled out the app last month. The new app allows users to create six-second videos that continually repeats or loops similar to GIF files but with audio. They can then share those videos with other websites, such as Twitter. Vine got off to a fast launch but was marred by a significant number of users uploading easily accessible pornographic videos to the new social network. Now when users attempt to download Vine, they are first prompted to confirm that they are at least 17 years old before the app begins installing. That's a good measure, but parents won't be happy to know that it's essentially just a procedural roadblock. Users can simply click "OK" regardless of their age. Twitter has made it harder to find explicit content by disabling many searchable tags that were being used for those types of videos. But as one Times user pointed out, pornographic material can be easily found just by adding "XXX" to the front of any search made on the app.