ks] Security Techniques a) [4 marks] What is meant by the term Denial of Service (DoS) attack? b) [2 marks] Give an example of a Denial of Service (DoS) attack. c) [6 marks] What is the main difference between a packet-level firewall and Intrusion Detection System (IDS)/Intrusion Prevention Systems? d) [8 marks] A laptop user is connected via WiFi to an access point which uses WPA2 security. The user is accessing their bank account via HTTPS protocol that employs SSL. The user realised that all their information is being encrypted twice once by the SSL implementation within the browser and then a second time by the WiFi interface card. The user thinks that this is unnecessary because once information has been encrypted it is secured and encrypting it again provides little improvement in security. Is it true that the double encryption is wasted effort in this example or are the two layers of encryption each valuable in their own right? Explain your answer by either showing that one of the layers could be removed without creating a security risk for the user, or by showing that both security layers are needed to provide the user with the security that thy truly require. (Hint: You should think about other threats in addition to threats against the bank account traffic.)