Recently we have seen 51% attacks on several CryptoNote coins. Zawy has developed new difficulty algorithm called LWMA (Linearly Weighted Moving Average), which should help fighting 51% attacks by only doubling the difficulty during the attack (about 15 blocks typically) and return to normal 10 blocks after the attack ends.
Coin developers are also required to reduce the allowed time drift (Future Time Limit, FTL) from 2 hours to 500 seconds.