1.0 Network Security

1.5 Identify commonly used default network ports

  • FTP

    File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and uses separate control and data connections between the client and server. Authentication is accomplished through the use of a clear-text sign-in protocol and is not considered to be secure.

    File Transfer Protocol first establishes, then maintains a control connection throughout the session over TCP port 21. Then a second connection is opened over TCP port 20 for data transfer.

  • SFTP

  • FTPS

  • TFTP

    Trivial File Transfer Protocol (TFTP) is a simple insecure protocol used to transfer files. It is typically implemented on top of the User Datagram Protocol (UDP) using port number 69. Packets are limited to a 512 byte limit and can be easily lost. When a packet smaller than 512 bytes is received, the server assumes the end of the file has been reached and closes the connection. Transmission is not guaranteed to be complete and has no provision for user authentication. TFTP is designed to be small and easy to implement, therefore, lacks most of the features of FTP. TFTP only reads and writes files (or mail) to or from a remote server, it cannot list directories. TFTP can be used for remote booting of devices without hard drives. Used in conjunction with a bootp server, the device receives its addressing information and the address of the TFTP server from which it should boot.


    Short for Telecommunications network, TELNET is a text based interface protocol that provides an insecure remote access to other computers. Telnet uses a command line interface and can be accessed in Windows from the Start menu by clicking <Start>, <Run>, then by typing: telnet (somesite) 23. Port number 23 is the default port used by telnet, but is usually optional and often not required.

  • HTTP

    Hypertext Transfer Protocol (HTTP) is an application-level protocol used to request and deliver web pages between a server and browser. HTTP is the foundation of data communication for the World Wide Web.


    Hypertext Transfer Protocol Secure (HTTPS) is a combination of Hypertext Transfer Protocol (HTTP) with SSL/TLS protocol. It provides encrypted communication and secure identification of a network web server. HTTPS connections are often used for payment transactions on the World Wide Web and for sensitive transactions in corporate information systems. HTTPS uses port 443 by default.

  • SCP

  • SSH

    Secure Shell (SSH) is a cryptographic remote login protocol for secure data communication over an unsecured network. Designed as a replacement for telnet and rlogin, which send information in plaintext, SSH client and server programs provide strong host-to-host and user authentication as well as a number of securely encrypted methods of communication to provide confidentiality and integrity of data. SSH supports data stream compression between the client and the server.

    There are two major versions of the SSH protocol in widespread use, SSH v1 and SSH v2. SSH v2 is more secure, and includes SFTP, which is similar to FTP, but is SSH v2 encrypted.

  • NetBIOS

    The Network Input Output System (NetBIOS) protocol was originally developed for IBM and Microsoft to support broadband network communication in the small to medium sized local area network environment. It is a Session layer protocol in the OSI model that establishes and manages communication between computers. Data transport services for NetBIOS are provided by NetBEUI.