Assignment
An organization has 2 server computers and a number of desktop computers and a few printers. All of them are connected together via an internal network, and the network is connected to the Internet via the border router of the organization. From the outside of the organization, on the Internet, only these 2 server computers are visible. One of them is the email server (IP address: e1.e2.e3.e4), and the other one is the web server (IP address: w1.w2.w3.w4). In other words, only these 2 server computers accept requesting incoming network traffic. All desktop computers are allowed to access the Internet, without any restriction. Therefore, they accept responding incoming network traffic, but not accepting any requesting incoming network traffic.
• Please design the network and draw the network diagram. You have the freedom to assume the internal network structure. In the diagram, in addition to the 2 servers, you should also include a few desktop computers and a printer. Please explain the rationale on why you put a computer or a printer in its designated location, 1 example for each location. A subnet (or a segment) is regarded as the same location. (hint: a firewall or a few firewalls, depending on your design, are needed to regulate the network traffic)
• Please write down the firewall rules to fulfil the access requirement of the organization. Please also explain the meaning of each firewall rule. If you have multiple firewalls, you should explain to which firewall each of the rules belongs. Below is a set of sample firewall rules. Please follow the sample firewall rule format to write down your firewall rules. Please also be advised that the order of the rules matters.
The meaning of the columns of the sample firewall rules in the screen dump is as follows. Please use only the information provided here and the textbook for your assignment. The information provided here is overly simplified from iptables manual to make the assignment manageable.
• action - ACCEPT means accepting the connection, and REJECT means not.
• prot - the protocol of the connection, e.g., tcp, udp, icmp, and all etc.;
• opt - please ignore;
• source - source IP address of the packet;
• destination - destination IP address of the packet, plus extra information, for example: o "tcp dpt: https" means that the TCP port of the destination host is https.
o state lists the connection state for the firewall to match on to perform the action of the rule. RELATED: the connection is new, but is related to another. connection already permitted; ESTABLISHED: the connection is already established.
o reject-with: please ignore. No need to include it in your assignment.
2. Please write a summary to briefly explain to senior managers, who know very little on computer security but have a general understanding of IT, on what a buffer overflow problem is and what the consequences of a buffer overflow problem could cause. What programming techniques the software development team should adopt to avoid buffer overflow problems in the software it develops.
Below is from a Nessus report on a computer.
• Pretending that the application is developed by the software development team of this organization, how to fix the problem.
• Accepting the recommendations given by the report, what action you should take? Assuming that this computer is one of the many desktop computers, and an automatic system for software updating is in operation. Write down the operational steps, by following the principle of "one, some, and many".
• Assuming that this computer is a server computer, please write a brief report to the senior managers, who know very little on computer security but have a general understanding of IT, explaining why the software Firefox (a web browser) should not be installed on the computer. In your report, you should use trusted information sources to explain to your senior managers on the best practices of operating system security administration. The senior managers trust only the text books of this unit, nothing else.