SMTP Simple Mail Transfer Protocol is the standard protocol for transferring mail between hosts over TCP A TCP connection is set up between a user agent and a server program The server listens on TCP

a. A packet filtering firewall is a type of firewall that operates at the network layer of the OSI model, inspecting individual packets of data as they are transmitted across a network. Packet filtering firewalls work by examining the header information of each packet that passes through them and comparing it against a set of predefined rules. These rules typically specify criteria such as source and destination IP addresses, protocol type, and port numbers. If a packet matches a rule, it is either allowed to pass through the firewall or blocked, depending on the action specified in the rule.

Packet filtering firewalls have several weaknesses. First, they are unable to inspect the contents of packets beyond the header information, which makes them vulnerable to certain types of attacks, such as those that use encrypted traffic or exploit vulnerabilities in the packet header. Second, they can be susceptible to IP spoofing attacks, where an attacker sends packets with a false source IP address in order to bypass the firewall. Finally, packet filtering firewalls can be difficult to configure and maintain, particularly as networks become more complex.

b. Rule A allows inbound SMTP traffic from external sources to internal hosts, as long as the source port is above 1023 and the destination port is 25. Rule B allows outbound SMTP traffic from internal hosts to external destinations, as long as the source port is 25 and the destination port is above 1023. Rule E denies all traffic that does not match any of the previous rules.

c. The attack will not succeed, as rule E will deny the incoming traffic from the outside world. Specifically, rule E denies all traffic that does not match any of the previous rules, and since there are no rules that allow traffic from port 5150 on a remote host to the web proxy server on port 8080 on the local host, the traffic will be blocked. None of the other rules in the rule set will be applied in this case