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Install Packet Tracer in Windows and Linux

Cisco Certified Network Associate certification has become must for anybody who wishes to start  a career in networking. This certification validates that you have the ability to install, configure and troubleshoot a network. You need  lot of practice for achieving success in this exam. Apart from the labs where you are getting trained for CCNA what if you had a chance to practice at home. Or what if you want to self learn for CCNA? Well for both of the questions above, Cisco Packet Tracer is the perfect answer. To quote from Cisco’s official website, Packet tracer is

“a powerful network simulation program that allows students to experiment with network behavior and ask “what if” questions.”

It further says,

“The simulation-based learning environment helps students develop 21st century skills such as decision making, creative and critical thinking, and problem solving. Packet Tracer complements the Networking Academy curricula, allowing instructors to easily teach and demonstrate complex technical concepts and networking systems design.”

Nothing could have defined that better. This software is available for free from Cisco’s website provided you are a registered Networking Academy student, alumni, instructor, or administrator. Even if you are not one among the above you could still get hold of this software, just google it.

Now I’m gonna show you how to install packet tracer in Windows and Linux.

1.Windows

Any installation in Windows is just clicks and mouse and the same applies to Packet tracer. Click on the exe file downloaded. The below screen appears. Select “I accept the agreement” and click on “Next”.

Setup will show the folder in which the program’s shortcuts will be created. If you want to change the folder, you can change it. Click on “Next”.

Then the program will ask whether to create a Desktop icon and create a Quick Launch icon. Make your own choice and click on “Next”.

Then the summary of the settings we selected is displayed. Click on “Install”.

The installation starts as shown below.

In seconds, installation gets completed and the below screen is shown. Click on “Finish”.

Then the below popup appears asking you to close or restart your computer. Click on “OK”.

As we selected Launch option, Packet tracer is automatically launched.

2. Linux

To install Packet Tracer in Linux, we need a .deb package of Packet tracer which can be downloaded from here. Now I am going to install it in Ubuntu Precise Pangolin (12.04). Download the above file to the desktop.

Start the terminal and see your current working directory by typing “pwd”. If the current directory is not desktop move to the Desktop directory using “cd”. After reaching the Desktop directory, type “ls” to see if the packet tracer binary is there.

Left click on the packet tracer .bin file displayed after typing “ls” above, the entire word will be selected. Then right click and select copy. Now type “chmod +x” and then hit “CTRL+SHIFT+V “to paste the text we copied above. Our command should look like this.

                       chmod +x  PacketTracer533_i386_installer-deb.bin

What chmod +x command does is that it gives all users permission to execute.

Then type “./PacketTracer533_i386_installer-deb.bin” in the terminal. This will start extracting the binary package.

Then terminal prompts us to hit Enter to read the End User License Agreement.  Enter.

After displaying a rather long EULA, terminal asks us if we accept the terms of EULA. Type “Y”.

Then system asks us for the sudo password. Type the password and hit Enter.

When the installation is finished, close the terminal, go to Dashboard, if packet tracer is not seen, type ‘pac’ in the search box. When Packet Tracer is shown, click on it.

A message box shows up saying that we are starting packet tracer for the first time and our files will be stored in a specific folder. Click on “OK”.

Another message box pops up. Click on OK”.

Packet tracer is started.

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Classification of ports by Nmap

Scanning plays a very important role in hacking a system. Scanning is a phase in which we  find out the ports which are open and the services listening on those ports. Nmap is the most popular port scanner being used security guys nowadays. However it is very important to understand classification of ports by Nmap while scanning. Nmap classifies ports into six states. They are, open, closed, filtered, unfiltered, open | filtered and closed | filtered. Let us find out when Nmap classifies ports into specific states. For this, I use two virtual machines,

1. Kali Linux as attacker (with IP 10.10.10.2)

2. XP as victim (with IP 10.10.10.3)

On the victim machine, Telnet server is running and an exception is provided for it in windows firewall.

1. Open

Nmap classifies a port as open if an application is actively accepting TCP connections, UDP datagrams or SCTP associations on this port.

When I perform a default Nmap scan from the attacker of port 23 of the victim,

Nmap  –p 23 10.10.10.3

The result I get is open. This is because the Telnet server is actively accepting connections.

2. Closed

Nmap classifies a port as closed when the port is accessible but there is no application listening on it.  On our victim machine, let’s stop the the telnet service as shown below.

Now when we perform the above scan again, the port is shown as closed because although the port is accessible we don’t have any application listening on it.(i.e telnet is stopped)

3. filtered

Nmap classifies a port as filtered when it can’t determine whether the port is open or closed because packet filtering prevents its probes from reaching the port. On our victim machine, let’s  select ‘Don’t Allow Exceptions’ option in the firewall settings.

When we perform the above scan once again, the port is classified as filtered because firewall filtering blocks the probes of Nmap. When Nmap classifies a port as filtered, it is most likely that a firewall is blocking our probes.

4. Unfiltered.

Nmap classifies a port as unfiltered when a port is accessible but it can’t determine whether it is open or closed. A port is classified as unfiltered only with the ACK scan.

Let’s start the telnet service again on our victim machine and allow an exception for telnet in the firewall.

Then let us perform the ACK scan.

nmap  -sA –p 23 10.10.10.3

The scan couldn’t determine whether the port is open or closed.

5. open | filtered

A port is classified as open | filtered when Nmap is unable to determine whether a port is open or filtered. This happens for scan types in which open ports give no response. The UDP,IP protocol, FIN, NULL and XMAS scans classify ports this way. Let’s go to our machine and once again block telnet using firewall.

And then perform FIN scan and NULL scan respectively.

The port is classified as open | filtered in both cases because Nmap can’t determine whether the port is open or filtered.

6. closed | filtered

Nmap can’t find out whether a port is closed or filtered. A port is classified this way only for IP IDLE scan. Now what is IDLE scan? Idle scan is a scan in which we use a zombie host to scan the victim. In our example, we use another host with IP 10.10.10.3 as a zombie to perform IDL scan on our victim.

In our victim, firewall is still blocking telnet. Let’s perform a IP IDLE scan.

nmap –sI  10.10.10.1 –p 23 10.10.10.3

The scan shows result as closed | filtered because it couldn’t determine whether a port is closed or filtered.

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Password cracking with Brutus

Hi everybody, today I’m gonna show you remote password cracking with Brutus. For the newbies, script kiddie is a person with little knowledge  of hacking or any programming languages and instead searches for automatic tools to hack the computers. In this scenario, script kiddie is using a Windows XP machine and two tools Zenmap and Brutus avilable for free to download. As you will see, Zenmap is used for scanning for any open ports of  live machines and Brutus is a password cracker.

Imagine I am the script kiddie, I  first find out my own computer’s  ip address by typing the command “ipconfig” in the command line.

The ip address of my system happens to be 10.10.10.1. I decide to scan the following range of ip addresses to look for any live hosts. In the target option, I specify ip address as 10.10.10.2-10 and I choose profile as intense scan to get maximum information about the target. After performing the scan, the results show that only one system 10.10.10.3 is alive.

The scan  also shows that the victim machine which is live  is running a ftp server and its operating system is Windows XP.

I decide to use Brutus to crack the remote FTP password. Brutus has both dictionary and bruteforce attack options. I decide to choose dictionary attack since it is faster than bruteforcing. Brutus comes with a built in username(users.txt) and password list(pass.txt).As the victim machine is running Windows xp which comes with a default administrator account, I decide to  add “administrator” to the users.txt file.

I choose type as FTP since I am about  to crack a FTP server.

Then I select the file pass.txt containing some common passwords and just hope to crack the password.

Then after starting the cracker, Brutus runs and gives one positive authentication result.

Username : administrator

Password: 123456

Then I try to log into the FTP server of the remote machine using cmd with the authentication result achieved above.

I successfully logged into the FTP server.Once I am into the remote machine I try some ftp commands but before that I change my local directory to Desktop.

Then I use DIR command to list the directories in the FTP server.

There are four directories in the FTP server:Detroit,Images,lena and users. I  go to the users directory using command cd users and then list the files in the directory by using command ls. There is one text file named users.txt in the directory.

I decide to download the file users.txt to my machine using the command get users.txt. Since I had set my local directory to desktop it will be downloaded to desktop.

Let’s see the contents of the users.txt file just downloaded. It contains some usernames and passwords.

In the same way, I enter into another directory of interest to me “Images” and download the only image present in it to my desktop.

In this way, I can download any number of files from the remote server to my local machine. That’s all for in password cracking with brutus.