Is Port 21 Secure? Fully Explained

You have files and images to transfer, and you want to know if Port 21 is secure?

Don’t worry, read on to learn all about Port 21 and FTP which is still used widely today.

Is Port 21 secure?

There are many ways to think about security and Port 21.

Port 21 is commonly associated with FTP. FTP has been assigned to Port 21 by the Internet Assigned Numbers Authority. The IANA also oversees global IP address allocation.

FTP is often thought of as a “not secure” file transfer protocol. This is mainly due to FTP sending data in clear text and offering an anonymous option with no password required. However, FTP is a trusted and still widely used protocol for transferring files. Many businesses rely on FTP for large file uploads and bulk file transfers.

But, what about Port 21?

Individuals, companies, and universities all use Port 21. It is a well-known port number. In fact, ports 1–1023 are considered the “well known” port numbers. Well known ports are essential for daily online interactions and data transfers.

Establishing a connection with a server via Port 21 does not automatically give your information away. Uploading and downloading files via FTP is done through a separate data channel, usually connecting to the server through Port 20. Meanwhile, your Port 21 connection allows you to enter FTP commands and browse file listings on the server.

Port 21 is not inherently insecure. And there are simple measures you can take to improve the security of your data when utilizing a Port 21 connection.

1. Require a password for all your file transfers. While this is common knowledge today, many people find passwords a hassle and tend to skip if not required. A weak username and password mean a less secure transaction no matter what port you use.

Enter credentials for FileZilla

2. It is also recommended that you limit IP addresses when using FTP and connecting through Port 21. Most FTP providers offer IP address whitelisting or blacklisting on your account as a simple security measure you can opt into.

The Server can Make a Difference.

FTP Server

First, keep your server up to date. Or, use an FTP service that is reliable and has the engineering staff who monitor and update their servers as needed.

This way you can count on a server kept in optimal condition without needing to find the time, money and I.T. staff to cover maintenance responsibilities.

An up to date server with the proper configuration means there are no known vulnerabilities when connecting and transferring files. Being proactive regarding server maintenance prevents issues such as security breaches, failures, and service outages.


Keys in open door

Packet Sniffers and Robot Scanners

A sniffer sniffs ALL ports and network traffic, searching for vulnerabilities, not just Port 21. These packet sniffers look at data packets that flow between computers or computers and servers over the internet. It is highly unlikely that scanners and sniffers specifically target Port 21. Agencies dealing with high-level or sensitive data would have private or registered ports they use along with alternative file transfer methods.

Individuals with malicious intent or who have some reason to desire access to your network will scan for all ports, looking for an opening. If you are using an alternate port instead of Port 21 for your FTP connections, it is likely that will be discovered just as quickly as if you had stuck with Port 21.

Looking at it from this angle, the port number is the least of the security issues.

Connecting to Port 21 / FTP server

Finally, when connecting, you send a signal to the server via the control channel which is used to authenticate the client in the client-server relationship. The control channel also facilitates your interactions with the server, and this channel stays open so you can browse your files while executing commands. Don’t leave the connection open when you are done uploading or downloading files. With FTP it is easy to enter a command to close out the session.

Learn more about FTP clients.



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Secure Cloud FTP platform provides full support for manual and automated transfers via web interface, FTP, FTPS and SFTP. Visit