Comment 14 for bug 498911

@konaya I just wrote a post in the forums of what I found to be the root cause of this issue. In my logs it appeared as if what caused the log file to grow so large was a brute-force attack. The log filling up is a result of the failed attempts to authenticate to your system's VNC server. After a certain number of failed attempts it appears as if the VNC server just starts rejecting the attempted connections without giving them a chance to authenticate (which is good). Luckily, if these are still happening then most likely they haven't hacked you yet. Check out my post if you are interested.

http://ubuntuforums.org/showpost.php?p=12507381&postcount=9