Introduction to FTP Protocol

Introduction to FTP

• FTP (File Transfer Protocol) is a standard network protocol for transferring computer files between a client and server on a network.
• It uses a client-server model; a client application connects to a server for file transfer.
• Primarily for file exchange, not interactive sessions like remote login.

Key Concepts and Functions

• Client-Server Architecture: FTP relies on a client application (e.g., FileZilla, command-line tools) interacting with a server application (often on a web server) holding files.
• Control Connection: A separate control connection manages transfer instructions (listing files, changing directories, data transfer). Data transfer occurs separately.
• Two Types of Connections:
  • Control Connection: Handles commands and responses (e.g., username/password, file listings).
  • Data Connection: Transfers the actual files.
• Passive and Active Modes: These modes control data transfer initiation:
  • Active Mode: Client initiates connection to the server's data port.
  • Passive Mode: Server initiates connection to the client's data port (preferred for firewalls).
• Port Assignments: Specific ports handle FTP communication:
  • Control connection typically uses port 21.
  • Data connection ports vary based on mode (active: 2000-2010; passive: higher ephemeral ports).
• File Transfer Commands/Instructions:
  • LIST: Displays files in a directory.
  • PWD: Shows the current directory.
  • CD: Changes the current directory.
  • PUT: Transfers a file from client to server.
  • GET: Downloads a file from server to client.

Security Considerations

• Insecure by Nature: FTP historically lacks built-in security features.
• Plaintext Authentication: Passwords and commands are often sent unencrypted, vulnerable to eavesdropping.
• Vulnerability to Attacks: FTP is susceptible to:
  • Man-in-the-middle attacks.
  • Brute-force attacks.
  • Data interception during transmission.

Alternatives and Improvements

• FTPS (FTP Secure): Uses TLS/SSL encryption for secure file transfer (an extension of FTP).
• SFTP (SSH File Transfer Protocol): More secure file transfer using SSH (Secure Shell), generally preferred for its security and ease of configuration.
• Web-based file transfer: Modern web-based file transfer solutions are alternatives for various needs.

Summary

• FTP is a basic file transfer protocol, but its lack of security is a concern.
• Modern systems often use secure alternatives (FTPS, SFTP) for stronger security.
• Understanding FTP's operation is still relevant for troubleshooting and legacy systems maintenance.