[eastforker]

And they always attack from behind. To counter that, the locals started wearing masks, like a halloween mask on the backs of their heads. The attacks stopped, for a while untill the tigers figured it out.

[marktwain]

Yes, it appears the mask trick works at least some of the time.

There are times when tigers attack from the front.

They prefer to attack from behind, because of the greater likelihood of success.

[rlmorel]

It is inborn behavior. Check out this short video (about a minute and half) of a guy who works with big cats. He puts a GoPro on his head pointing backwards, and then turns his back on the big cats...very interesting.

LINK: Never Turn Your Back On Big Cats