EC0-350 Question #10: Real Exam Question with Answer & Explanation

Samuel is the network administrator of DataX Communications, Inc. He is trying to configure his firewall to block password brute force attempts on his network. He enables blocking the intruder's IP address for a period of 24 hours' time after more than three unsuccessful attempts. He is confident that this rule will secure his network from hackers on the Internet. But he still receives hundreds of thousands brute-force attempts generated from various IP addresses around the world. After some investigation he realizes that the intruders are using a proxy somewhere else on the Internet which has been scripted to enable the random usage of various proxies on each request so as not to get caught by the firewall rule. Later he adds another rule to his firewall and enables small sleep on the password attempt so that if the password is incorrect, it would take 45 seconds to return to the user to begin another attempt. Since an intruder may use multiple machines to brute force the password, he also throttles the number of connections that will be prepared to accept from a particular IP address. This action will slow the intruder's attempts. Samuel wants to completely block hackers brute force attempts on his network. What are the alternatives to defending against possible brute-force password attacks on his site?