WPS has been shown to easily fall to brute-force attacks. A major security flaw was revealed in December 2011 that affects wireless routers with the WPS feature, which most recent models have enabled by default. The flaw allows a remote attacker to recover the WPS PIN and, with it, the network's WPA/WPA2 pre-shared key in a few hours. Users have been urged to turn off the WPS feature, although this may not be possible on some router models.