“Most Wi-Fi routers susceptible to hacking through security feature”(Naked Security),
Stefan Viehböck, an independent security researcher, published a paper on Boxing Day titled “Brute forcing Wi-Fi Protected Setup” to his WordPress blog disclosing a weakness in the configuration of most consumer/SoHo Wi-Fi routers.
(snip)
So you have now reduced the difficulty of brute forcing the PIN down to 104 (10,000) plus 103 (1,000) or 11,000 possibilities.
Some of the routers Viehböck tested did seem to implement a mechanism to slow down the brute forcing, but the worst case scenario allowed him to acquire the keys within 44 hours.
Compared with attempting to attack WPA2-PSK directly, this is a cheap and effective attack.
As the sub-title of Viehböck’s paper states “When poor design meets poor implementation” security is the loser.