Facebook has spent $40,000 (25,000 pounds) in the first 21 days of a program that rewards the discovery of security bugs.

The bug bounty program aims to encourage security researchers to help harden Facebook against attack.

One security researcher has been rewarded with more than $7,000 for finding six serious bugs in the social networking site.

The program runs alongside Facebook's efforts to police the code it creates that keeps the social site running.

A blog post by Facebook chief security officer Joe Sullivan revealed some information about the early days of the bug bounty program.

He said the program had made Facebook more secure by introducing the networking site to "novel attack vectors, and helping us improve lots of corners in our code".

The minimum amount paid for a bug is $500, said Mr Sullivan, up to a maximum of $5000 for the most serious loopholes. The maximum bounty has already been paid once, he said.

Full story: BBC News