The Friendly Robber is an official variant for The Settlers of Catan and its expansions. It was created by Klaus Teuber and included in Catan: Traders & Barbarians.
In the Manual
What's going on in the forest of Catan? Strange stories are coming out of the dark woods of the Black Forest, hinting that Isebold and his dreaded robbers have disappeared without a trace, and that a young lad has taken his place. His name is said to be Rob de Hood, and supposedly he is only taking from rich travelers. Poor devils are allowed to move on...
Rules
The Friendly Robber is yet another way to add flavor in any Catan game. It simply adds an additional rule, regarding The Robber. The additional rule states that when a "7" is rolled or a knight card is played, the robber may not be moved to a terrain hex that is adjacent to a settlement/city of a player who only has 2 Victory points. If, because of that rule, the robber has no valid terrain hex to move to, the robber moves to (or remains on) the desert hex. In this case, a resource card may not be taken from any player who only has 2 Victory points. When using this rule, you still lose half of your resource cards when a seven "7" is rolled and you have more than 7 resource cards.
Tips for playing this variant
This variant should always be used when playing in a family circle, particularly when children are participating in the game.