Laboratory 2 PRACTICE EXAMINING TRAFFIC WITH A PROTOCOL ANALYZER The purpose of this lab is to practice examining traffic using a protocol analyzer and recognize a SYN attack. The SYN flood attack is one of the common Denial of Service (DoS) attacks in the Internet. In the SYN flood attack, an attacker sends a large number of SYN packets to the server, ignores SYN/ACK replies and never sends the expected ACK packet. Basically, the attacker overwhelms the server with many half-established connections and exhausts the server resources, and hence the attack is known as a DoS attack. The tool you will be using is known as Wireshark, a well-known open source packet analyzer. The exercise will demonstrate that recognizing an attack requires sophisticated tools (such as Wireshark) and knowledge of the domain (TCP/IP network). Assignment: 1. Obtain a trace file of the TCP handshake process. Download the attached files: "tcpshake.cap," "tcpshake.prn" (TCP: Handshake Process) and "tcp-syn-attack.cap," "tcp-syn-attack.prn," (TCP: TCP SYN Attack). The .prn file is a text file, and you can read it with Notepad or Wordpad. It contains a formatted "report" with information on each packet. The .cap file is in the proprietary Sniffer format. Opening this file produces a graphic representation of the same information. You can read .cap files with Wireshark/Ethereal, a public domain analyzer. 2. Obtain Wireshark Follow the link to Wireshark from  http://www.wireshark.org  (or  http://www.filehippo.com/download_wireshark/ ) and download the version 2.0.5 or a previous version (the current stable release of Wireshark is 2.0.5). Depending on the version, release and OS you might find the options in different places. On the Wireshark home page, follow the link to Download. For Windows, you may download and install "wireshark-win32-2.0.5.exe." Select all installation options. (Note: These files are about 13-22MB.) On the same page you can find also the documentation ( http://www.wireshark.org/download.html ). If you use a packet driver, Wireshark can both capture packets and read trace files of packets that have already been captured. However, the packet driver must access parts of your operating system that some students may not have access to. That is the reason why this is not a packet capturing exercise. However, you should learn to capture packets yourself if you can. The packet driver you will need is winpcap. It is available at  http://www.winpcap.org/install/ . However, you do not need winpcap for the exercise you are going to do now. 3. Read the tcpshake.cap trace file. Become familiar with Wireshark's interface. Run Wireshark from the shortcut that is now on your desktop. Click File|Open and uncheck all the name resolution options at the bottom of the dialog box. Type the path to tcpshake.cap, or navigate to it using the top part of the dialog box. (This interface may take a few trials to get used to.) Explore the trace in the three panes of the analyzer. .

1. Laboratory 2
PRACTICE EXAMINING TRAFFIC WITH A PROTOCOL
ANALYZER
The purpose of this lab is to practice examining traffic using a
protocol analyzer and recognize a SYN attack. The SYN flood
attack is one of the common Denial of Service (DoS) attacks in
the Internet. In the SYN flood attack, an attacker sends a large
number of SYN packets to the server, ignores SYN/ACK replies
and never sends the expected ACK packet. Basically, the
attacker overwhelms the server with many half-established
connections and exhausts the server resources, and hence the
attack is known as a DoS attack.
The tool you will be using is known as Wireshark, a well-known
open source packet analyzer. The exercise will demonstrate that
recognizing an attack requires sophisticated tools (such as
Wireshark) and knowledge of the domain (TCP/IP network).
Assignment:
1. Obtain a trace file of the TCP handshake process.
Download the attached files: "tcpshake.cap," "tcpshake.prn"
(TCP: Handshake Process) and "tcp-syn-attack.cap," "tcp-syn-
attack.prn," (TCP: TCP SYN Attack). The .prn file is a text file,
and you can read it with Notepad or Wordpad. It contains a
formatted "report" with information on each packet. The .cap
file is in the proprietary Sniffer format. Opening this file
produces a graphic representation of the same information. You
can read .cap files with Wireshark/Ethereal, a public domain
analyzer.
2. Obtain Wireshark
Follow the link to Wireshark from
http://www.wireshark.org
(or
http://www.filehippo.com/download_wireshark/
) and download the version 2.0.5 or a previous version (the
current stable release of Wireshark is 2.0.5). Depending on the

2. version, release and OS you might find the options in different
places.
On the Wireshark home page, follow the link to Download. For
Windows, you may download and install "wireshark-win32-
2.0.5.exe." Select all installation options. (Note: These files are
about 13-22MB.) On the same page you can find also the
documentation (
http://www.wireshark.org/download.html
).
If you use a packet driver, Wireshark can both capture packets
and read trace files of packets that have already been captured.
However, the packet driver must access parts of your operating
system that some students may not have access to. That is the
reason why this is not a packet capturing exercise. However,
you should learn to capture packets yourself if you can. The
packet driver you will need is winpcap. It is available at
http://www.winpcap.org/install/
. However, you do not need winpcap for the exercise you are
going to do now.
3. Read the tcpshake.cap trace file. Become familiar with
Wireshark's interface.
Run Wireshark from the shortcut that is now on your desktop.
Click File|Open and uncheck all the name resolution options at
the bottom of the dialog box. Type the path to tcpshake.cap, or
navigate to it using the top part of the dialog box. (This
interface may take a few trials to get used to.)
Explore the trace in the three panes of the analyzer. These three
panes are standard to most analyzers. They are the summary
pane, the protocol tree pane, and the hex pane.
Explore the preferences and configuration options in Wireshark.
Share your findings with the class.
Print a packet or any part of a packet you are interested in.
4. Read the tcp-syn-attack.cap file and answer the following 10
questions:
Is this a two-way conversation?
Are there any ACK's?

3. How long is the data portion of each packet? Why?
Why is the sequence number zero (seq=0) in every packet?
Why do the port numbers change in every packet?
Look at the "Time" column in the summary pane. How do you
interpret it?
Click the "View" menu and select "Time Display Format".
"Seconds since beginning of capture" is checked. Select
"Seconds since Previous Captured Packet". How frequently are
these packets being sent?
Where in the protocol tree pane would you find the protocol
"Type" field?
Look in the flags section of the transport layer (Transmission
Control Protocol" in the protocol tree section for one of the
packets. What flags are set?
How does a SYN attack deny service?
Post your answer to the assignment folder under LAB2 (due
date: 11/13).