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48730-32548, Cyber Security Week-5

Lab Overview

The learning objective of this lab is to gain first-hand experience on TCP/IP vulnerabilities, as well as
attacks against these vulnerabilities. The vulnerabilities in the TCP/IP protocols represent a special genre
of vulnerabilities in protocol designs and implementations. They provide an invaluable lesson as to why
security should be designed in from the beginning, rather than being added as an afterthought. Moreover,
studying these vulnerabilities help students understand the challenges of cyber security and why many
cyber security measures are needed. Vulnerabilities of the TCP/IP protocols occur at several layers. This
lab is designed to learn them step-by-step.

Lab Environment Setup

To conduct this lab, we require all the three virtual machines: Server, Client and Attacker. The tools being
used for this lab are Wireshark/Tshark, Netwox/Netwag.

Netwox/Netwag

We need tools to send out network packets of different types and with different contents. We can use
Netwag to do that. However, the GUI interface of Netwag makes it difficult for us to automate our process.
Therefore, we strongly suggest that you use its command-line version, the Netwox command, which is
the underlying command invoked by Netwag.

Netwox consists of a suite of tools, each having a specific number. You can run the command as following
(the parameters depend on which tool you are using). For some of the tools, you have to run it with the
root privilege:
➢ netwox [parameters ...]

If you are not sure how to set the parameters, you can look at the manual by issuing "netwox --
help". You can also learn the parameter settings by running Netwag for each command you execute from the
graphic interface, Netwag actually invokes a corresponding Netwox command, and it displays the parameter
settings. Therefore, you can simply copy and paste the displayed command.

Wireshark Tool.

You also need a good network-traffic sniffer tool for this lab. Although Netwox comes with a sniffer, you
will find that another tool called Wireshark is a much better sniffer tool.

Both Netwox and Wireshark can be downloaded. If you are using our pre-built virtual machine, both tools
are already installed. To sniff all the network traffic, both tools need to be run with root privilege.

Tshark Tool.

It is a terminal based network packet analyzer. You also need a good command line network-traffic sniffer
tool for this lab.

48730-32548, Cyber Security Week-5

The lab is based on documents “SEED Labs” provided by Wenliang Du, Syracuse University

Lab Tasks

In this lab, you need to conduct attacks on the TCP/IP protocols. You can use the Netwox or Netwag,
Wireshark, Tshark tools in the attacks. All the attacks are performed on Linux operating systems. However,
you can also conduct the same attack on the other operating system and compare the observations after
lab classes. You are supposed to use all the three Virtual Machines for the experiments.

To simplify the “guess” of TCP sequence numbers and source port numbers, we assume that attacks are
on the same physical network as the victims (Think of where such attacks may happen?). Therefore, you
can use sniffer tools to get that information. The following is the list of attacks that need to be
implemented and studied in this lab.

Before starting the task, disconnect the internet from the Server VM.

Task 1: SYN Flooding Attack

SYN flood is a form of DoS attack in which attackers send many SYN requests to a victim’s TCP port, but
the attackers have no intention to finish the 3-way handshake procedure. Attackers either use spoofed IP
address or do not continue the procedure. Through this attack, attackers can flood the victim’s queue that
is used for half-opened connections, i.e. the connections that has finished SYN, SYN-ACK, but has not yet
got a final ACK back. When this queue is full, the victim cannot take any more connection. Following figure
illustrates the attack.

48730-32548, Cyber Security Week-5

The lab is based on documents “SEED Labs” provided by Wenliang Du, Syracuse University

The size of the queue has a system-wide setting. In Linux, you can check the system queue size setting
using the following command:
➢ sysctl -q net.ipv4.tcp_max_syn_backlog
You can use command netstat -na to check the usage of the queue, i.e., the number of half opened
connection associated with a listening port.

For this task, Netwag Tool 76 will be used to conduct the attack, and tshark tool to capture the packets.

Steps:

1. As SYN flood produces a lot of traffic in the VM due to high speed, Wireshark might
crash. It is recommended to use “tshark” by entering “sudo tshark” on Terminal of the
Client VM.

2. Then go to Attacker VM and start Netwag by entering “sudo netwag” on the Terminal.
3. Select 76: Synflood.
4. Enter the details and click run it. (Screenshot required)
5. Observe the captured packets on Client VM. (Screenshot required)

Questions:

1. Observe the attack and take screenshots of the attack scenario.
2. Comment on your observation.
3. Categorize this attack in terms of severity and how it is linked to the DoS attack
48730-32548, Cyber Security Week-5

The lab is based on documents “SEED Labs” provided by Wenliang Du, Syracuse University

Task 2: ARP cache poisoning

The ARP cache is an important part of the ARP protocol. Once a mapping between a MAC address and an
IP address is resolved as the result of executing the ARP protocol, the mapping will be cached. Therefore,
there is no need to repeat the ARP protocol if the mapping is already in the cache. However, because the
ARP protocol is stateless, the cache can be easily poisoned by maliciously crafted ARP messages. Such an
attack is called the ARP cache poisoning attack.

Normal Scenario:
Attackers may use spoofed ARP messages to trick the victim to accept an invalid MAC-to IP mapping, and
store the mapping in its cache. There can be various types of consequences depending on the motives of
the attackers. For example, attackers can launch a DoS attack against a victim by associating a non-existent
MAC address to the IP address of the victim’s default gateway; attackers can also redirect the traffic to
and from the victim to another machine, etc.

Attack Scenario:
48730-32548, Cyber Security Week-5

The lab is based on documents “SEED Labs” provided by Wenliang Du, Syracuse University
5

For this task, Netwag Tool 80 is required to conduct the attack, and wireshark tool to capture the packets.

HINTS: In this task, you need to demonstrate how the ARP cache poisoning attack work. In Linux we can
use the command arp -a to check the current mapping between IP address and MAC address.

Steps:

1. In Server VM, run “arp -a” on terminal to get the ARP Information (MAC Table).
(Screenshot Required)
2. Open Netwag on Attacker VM by entering “sudo netwag” on the Terminal.
3. Select Tool 80: Periodically Send ARP Replies.
4. Add the fake MAC address and IP address and select the interface. (Screenshot
Required)
5. Click “Run It”.
6. Check the MAC Table on Server VM and look for the change in MAC address for IP
address provided in the Netwag tool 80. (Screenshot required)

Questions:
1. Observe the attack and take screenshots of the attack scenario.
2. Comment on your observation.
3. Briefly describe how you can mitigate this attack.

Task 3: ICMP Redirect Attack

The ICMP redirect message is used by routers to provide the up-to-date routing information to hosts,
which initially have minimal routing information. When a host receives an ICMP redirect message, it will
modify its routing table according to the message.

Because of the lack of validation, if attackers want the victim to set its routing information in a particular
way, they can send spoofed ICMP redirect messages to the victim and trick the victim to modify its routing
table.

For this task, Netwag Tool 86 is required to conduct the attack, and wireshark tool to capture the packets.

HINTS: In this task, you should demonstrate how the ICMP redirect attack works, and describe the
observed consequence. To check the routing information in Linux, you can use the command route

Steps:

1. Open Wireshark on Client VM by entering “sudo wireshark” in the terminal.
2. Select the interface and set “icmp” as filter and click “Apply”.
3. Open a new terminal on Client VM and ping the server. (Screenshot required)
4. Go to Attacker VM, run Netwag using the terminal.
5. Select the interface and “spoofip: IP spoof initialization type”. Input the required IP
address into “gw: new gateway” and “src-ip: source IP address”. (Screenshot Required)
6. Click “Run It”.
7. Go back to Client VM, check the Wireshark output. (Screenshot Required)

48730-32548, Cyber Security Week-5

The lab is based on documents “SEED Labs” provided by Wenliang Du, Syracuse University

Questions:
1. Observe the attack and take screenshots of the attack scenario.
2. Comment on your observation.
3. Briefly describe how you can mitigate this attack.