Information Assurance and Security Nick Rosasco

Karthikreddy Nalapatla
3884252

What is a Port Number A port number is a way to identify a specific process to which an internet or other network message is to be forwarded when it arrives at a server. For the transmission control protocol and the user Datagram protocol, a port number is a 16 bit integer that is put the header appended to a message unit. This port number is passed logically between the client and the server transport layers and physically between the transport layer and the Internet Protocol layer and it will forward it on to the other layers. For an example, a request from a client to a server on the internet may request a file to transfer from the host File Transport Protocol (FTP) server. In order to pass that request which is passed by us to the FTP in the remote server, the Transmission Control Protocol (TCP) identifies the port number which is of 16 bit length, then that port will forward the request to the FTP Server.
FTP and the FTP Port Number The File Transfer Protocol (FTP) is a standard network protocol used to transfer computer files from one host to the other host over a TCP – based network, for an example Internet. FTP is a Client – server architecture and uses a separate control and the data connections between the client and the server. The model of the FTP is shown below.

Fig 1: File Transport Protocol Model Executing an FTP port connection through a client is two – stage process requiring the use of two different ports. Once the user enter the name of the server and the login details in the authorization fields of the Client FTP, the FTP connection will be established and the FTP control port will get opened, by default the FTP uses the Port number 21 for sending the commands and then the second connection to the server will be made by the client, which will be followed by the FTP server from the port for sending of the data, by default for the sending of the data FTP uses the port number 20.
Functionality of Port 20 and Port 21 TCP and IP are the two major protocols on which the internet runs very smoothly. Where the TCP manages data to Transfer and while the IP directs the traffic to the internet address. FTP is an underling of the TCP and the shuttles files back and forth between the FTP Server and the FTP Client. Because FTP requires two ports 20 and port 21 to be open to exchange the large files of the information. As the clients make a TCP control connection to the FTP server port 21 which will be remained opened during the transport process. The FTP server opens a second connection that is the data connection from the server port 20 to the client system. If a client encounters a problem when connecting to the FTP server, the first thing we need to check is the FTP data transfer mode. Depending on certain network configuration, this mode should be either active or passive.
Active Mode of FTP Among the two modes of FTP, the active mode when the user connects from a random port on the FTP client to port 21 on the server, it sends the PORT command, specifying what the client – side port of the server should be connected too and this port will be used later on for the data channel. And now the server connects from the port 20 to the client port and designated for the data channel. Once the connection is established, file transfers are then the made through the client and the server ports.

Fig 2: Active Mode of the FTP Channel
Passive Mode of FTP In the passive mode client connects from a random port 21 on the server and issues the PASV command. The server replies and indicates that port it has opened for the data transfer. And now the client connects from the random port to the random port which has been specified in the server’s response. Once the connection is established, the data transfer is made through this client and the server ports. The better understanding of the passive port can be know from the following fig.

Fig 3: Passive Mode of the FTP
Security Issues with the FTP There is no doubt that FTP is an Simple and easy to understand but it has its own concerns when it comes to the Security issues, most of the Hackers thinks that it’s very easy to get into the FTP models. The some issues with the FTP is as follows. * Packet Capture
The data transfer with the FTP is in the clear text, any of the sensitive information such as usernames and the passwords can be easily read in the network packet capture techniques such as packet sniffing. A packet sniffing is like a computer program which can capture the transmitted data packets and decodes the packets data and exposes what is contained in the various fields of the packets. * Port Stealing
When the operating system assign a dynamic port numbers in the particular order or in the pattern, the attackers can easily decode the pattern and identify the next port number which will used. And the attacker have an illegal access into the ports and its port numbers.
Impact on the services in the term of CIANA * Integrity : For every service which transfer the data, integrity plays a major role in the sending the data between the client server and the host server, but the security issue with the FTP port 20 and port 21 gives an serious impact on the service, because of its failure to secure the Firewall. Which is a serious security concern of the FTP. The best way of providing the integrity to the FTP is to provide some serious Firewall settings which prevents the other ports to connect into the network. * Availability: FTP is very easy to configure and understand the process of the transmitting the data from client end to the host end. There are many private and public sector companies still using the FTP ports for transmitting the data, but the security issue of the TROJANS are showing the serious impact on the availability. The traojan can be used to escalate privileged and cause some major security issues like Blade runner, EvilFTP and the FORE, Larva. * Confidentiality: In any of the model the confidentiality is important but there is a serious concern on the confidentiality when we use an FTP PORT 20 and 21, by using an packet capture are by using the port stealing an attacker can steal the data of the user and can access the data illegally, so there is no confidentiality in the network. We can overcome this confidentiality by updating the FTP to the MFT which provides more security to the system, as it carry out the ad hoc file transfer and we can monitor the file transfer process in the real time. Which gives a lot of confidentiality to the system and the end user can feel secure about the information which the user is getting.

Conclusion Although the FTP system is very easy to understand and also which makes the life easier for the users to transfer the data, but there are some serious security concerns which one has to look at and we need to update the system. In my few by using the MFT we can overcome most of the security issues which are provided by the FTP and its ports.

References 1. Oh, S. (n.d.). File Transfer and Access. Retrieved February 23, 2015, from http://www.csun.edu/~jeffw/Semesters/2006Fall/COMP429/Presentations/Ch25-FTP.pdf 2. Egli, P. (n.d.). INTRODUCTION TO FTP, THE INTERNET'S STANDARD FILE TRANSFER PROTOCOL. Retrieved February 23, 2015, from http://www.indigoo.com/dox/itdp/07_FTP-TFTP/FTP.pdf 3. Explanation of the FTP and SFTP protocols. (n.d.). Retrieved February 23, 2015, from http://www.wise-ftp.com/know-how/ftp_and_sftp.htm 4. Karrick, S. (n.d.). FTP PORT 21 1'FRIEND OR FOE" Retrieved February 23, 2015, from http://pen-testing.sans.org/resources/papers/gcih/ftp-port-21-friend-foe-support-cyber-defense-initiative-103422 “ I have neither given nor received nor I have tolerated others used of unauthorized aid”