Bluring the post content!
 

Hello,
I have seen this feature in some forums which is using vBulletin but i have not remember any name. They are forcing to register users with using blur technology. It converts all posts to image with a heavy blur effects and so force users to register this system.

Are there any modification or plugin to do this process?

Thank you so much :)

It would help if we can see an example of this so we can see exactly what they are doing.

simple CSS wrapped in a conditional

http://css-tricks.com/fun-with-blurred-text/

It depends on how serious you are about hiding the stuff. If you use the CSS solution posted above I think users can just view the page source and see the text (and maybe you're ok with that). If you really are trying to hide your content you'd probably need to do something on the server.

If someone really wants to take the time to do this, look at imagecreate and imagepng in the PHP manual.