What is File Transfer Protocol (FTP) and how does it work?

File transfer protocol, or FTP, is one of the oldest methods for moving files between computers over a network. It was built in the early days of the internet and has been a core part of web infrastructure ever since. Web developers use it to upload site files to a server. System admins use it to move large data sets between machines. Hosting providers rely on it to give clients direct access to their server directories.

But FTP was designed in an era when network security was not a priority. It sends data, including usernames and passwords, as plain text. Anyone on the same network can intercept that traffic with basic tools. That single weakness has pushed most professionals toward safer alternatives like SFTP and FTPS.

This article breaks down how FTP works, what makes it vulnerable, and when it still makes sense to use it.

What is File Transfer Protocol (FTP)?Link to heading

FTP (File Transfer Protocol) is a standard communication protocol that allows files to be transferred between computers over a TCP/IP network, including the Internet.

FTP operates by creating two separate connections between devices. One connection is used to send commands and receive responses between the client and server, while the second connection handles the actual file transfer. During an FTP session, systems use commands such as “send”, “get”, “change directory”, and “transfer” to manage files and control communication.

FTP supports three file transfer modes: stream, block, and compressed. In stream mode, data is sent as a continuous flow without dividing it into separate sections. Block mode breaks the data into individual blocks before transmission. In compressed mode, FTP reduces the size of the data using the Lempel-Ziv compression algorithm to improve transfer efficiency.

>>> Learn more: What is Transmission Control Protocol? Key features of TCP

What is FTP used for?Link to heading

One of the biggest advantages of FTP is its ability to transfer large files. While common file-sharing methods work well for smaller documents, FTP can handle files that are hundreds of gigabytes in size while maintaining a stable transfer process.

File Transfer Protocol also helps improve productivity by allowing multiple files to be transferred in a single operation. Instead of uploading or downloading files one at a time, users can select a group of files and transfer them together, saving time and reducing manual work.

For example, if a company needs to send a large collection of files from its main office to a branch location, FTP can start the transfer immediately and continue running in the background.

How many types of FTP are there?Link to heading

Although FTP serves many file transfer needs, it is generally divided into three main types.

FTPLink to heading

Standard FTP, often called plain FTP, does not use encryption to protect data during transmission. It typically uses port 21 and remains widely supported by many servers and applications.

FTPSLink to heading

FTPS, or FTP Secure, adds SSL/TLS encryption to the FTP protocol. This encryption helps protect data and login credentials while they are transmitted across a network. FTPS was one of the earliest methods developed to provide a more secure version of FTP.

FTPESLink to heading

FTPES stands for File Transfer Protocol over Explicit TLS/SSL. It begins as a standard FTP connection on port 21 and then upgrades the session to use TLS/SSL encryption through specific commands. Because FTPES is often easier to use with firewalls, many organizations choose it as a secure alternative to traditional FTP.

>>> Learn more: What is an SSL port? Default ports, setup & troubleshooting

How to use FTPLink to heading

There are three common ways to use FTP for transferring files between a client and a server:

• Using a web browser: A web browser can access FTP servers directly, allowing users to download files without installing additional software. This method is simple and suitable for basic file access.
• Using an FTP client: A graphical FTP client, such as FileZilla or WinSCP, provides an interface for connecting to FTP servers. These applications make it easy to upload, download, organize, and manage files.
• Using the Command Line: Most operating systems include built-in FTP commands. Users can connect to FTP servers and transfer files through a command-line interface without using third-party software.

What is an FTP port?Link to heading

An FTP port serves as a communication endpoint between an FTP client and an FTP server. Network applications use ports to establish connections and exchange data. FTP relies on specific ports to manage file transfers and communication between systems efficiently.

FTP vs SFTPLink to heading

FTP stands for File Transfer Protocol, while SFTP stands for Secure Shell File Transfer Protocol. SFTP transfers files through SSH, which creates a secure connection and can provide access to remote shell accounts. A shell account is an account located on a remote server.

The main difference between FTP and SFTP is security. Standard FTP does not provide a secure channel for file transfers, while SFTP encrypts the connection. FTP also uses two channels to transfer data, while SFTP uses only one. Their default ports are different as well. FTP usually uses port 21, while SFTP uses port 22 for inbound communication.

The way each protocol transfers data is also different. SFTP uses a tunneling method to move data through a secure connection. FTP uses direct transfer, which makes it less secure when encryption is not added.

FTP vs HTTPLink to heading

Hypertext Transfer Protocol (HTTP) and FTP are both application-layer protocols that can transfer files between systems, but they work in different ways. HTTP is stateless, which means it does not store session data for use in later requests. Because of this, HTTP can support many sessions at the same time.

FTP is stateful, which means it keeps information about the client and uses it in later requests. Since FTP maintains session details, it can support fewer simultaneous sessions than HTTP. Depending on the use case, HTTP can be a more efficient method for data transfer, even when network bandwidth is the same.

Another key difference is authentication. FTP usually requires client authentication before files can be transferred. HTTP does not always require client authentication. HTTP also uses common ports that are easier for firewalls to handle, while FTP can be more difficult to manage because of its connection behavior and port usage.

FTP vs MFTLink to heading

Managed file transfer, or MFT, is a more modern approach to file transfer when compared with FTP. FTP still works in many situations, but it was not built for the complex security risks businesses face today. There have also been official warnings about the risks of using File Transfer Protocol, including versions secured with SSL or SSH.

As its name suggests, managed file transfer includes management tools, compliance controls, and security features. These features help make data transfers safer and support organizations that must meet strict data protection rules, especially those that handle sensitive information such as medical records or financial data. 

Standard File Transfer Protocol can expose transfers to risks such as eavesdropping attacks or banking Trojans that target financial institutions.

Although it is possible to manually add security and management features to FTP, MFT saves time and reduces complexity. For example, if two users were sending sensitive project files through an insecure FTP connection, an attacker could intercept the communication before it reached the FTP port. The stolen information could then be sold or used by a competitor, creating a serious business risk.

How to change FTP port numbersLink to heading

Application servers usually have default port numbers, but these numbers can be changed in two common ways:

1. Go to the settings page of your FTP application and update the port number there.
2. Add the port number directly to the FTP server address. To do this, place a colon and the new port number at the end of the FTP server address, before the “/” if the address includes one. For example: ftp://mydomain.com:####/, where each “#” represents a digit.

Benefits of FTP Link to heading

File Transfer Protocol offers several practical benefits for moving files between systems. It allows users to transfer multiple files and directories at the same time instead of sending each item one by one.

FTP also supports transfer recovery. If the connection drops during a file transfer, users can resume the process rather than starting again from the beginning. Another useful feature is queueing. Users can add files to a transfer queue, and FTP will process those files later in order.

FTP does not usually place strict limits on the number of files or the maximum file size that can be transferred, making it useful for handling large folders or bulk transfers. It also supports scheduled transfers, which helps users automate file movement at specific times. In addition, FTP allows users to cancel an active transfer when needed.

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Security challenges of FTPLink to heading

FTP was not built with security as a primary goal. As a result, it does not encrypt data during transmission. If an attacker intercepts an FTP connection, they can view or modify the transferred information without having to bypass encryption. Even when files are stored in FTP-based cloud environments, a security breach at the provider's end could expose sensitive data.

Because File Transfer Protocol sends data in plain text, it is vulnerable to several types of cyberattacks, including spoofing, packet sniffing, and brute-force attacks. Attackers can also use port scanning tools to identify FTP services and look for weaknesses that can be exploited.

One of FTP's biggest security issues is its use of clear-text passwords. Usernames and passwords are transmitted exactly as they are entered, without encryption or masking. For example, a password such as “Kary1996” would travel across the network in its original form. More secure protocols encrypt credentials before transmission, making them unreadable to anyone who intercepts the traffic. 

Since standard FTP does not provide this protection, attackers have a much easier time capturing login credentials and gaining unauthorized access.

ConclusionLink to heading

File Transfer Protocol has played a major role in file sharing and server management for decades. However, FTP was created long before modern cybersecurity threats became a concern, which is why standard FTP lacks the encryption and security controls expected today.

Understanding how File Transfer Protocol works, its strengths, and its limitations can help you choose the right solution for your environment. While FTP remains useful in certain situations, organizations that handle sensitive data should consider more secure alternatives such as SFTP, FTPS, or managed file transfer platforms to better protect their information.