10 MQTT Security Best Practices

MQTT is a lightweight publish/subscribe messaging protocol frequently used in IoT applications. Due to its small footprint and low bandwidth requirements, MQTT is often used in resource-constrained environments.

However, the lightweight nature of MQTT also makes it vulnerable to security threats. In this article, we will discuss 10 MQTT security best practices that can help you secure your MQTT deployment.

1. Use TLS

TLS is a cryptographic protocol that provides communication security over the internet. It’s the successor to SSL, and it’s used in a wide variety of applications, including web browsers, email, instant messaging, and VoIP.

When using MQTT, TLS ensures that all data exchanged between the client and broker is encrypted. This prevents eavesdropping and tampering with messages, and it helps to ensure the privacy of communications.

TLS is also important for authentication. When using TLS with MQTT, the client can be authenticated using a digital certificate. This helps to ensure that only authorized clients are able to connect to the broker and exchange messages.

Digital certificates can be obtained from a number of different sources, including public Certificate Authorities (CAs) or private Certificate Authorities (PCAs). When choosing a CA, it’s important to select one that is reputable and has a good reputation for providing secure certificates.

It’s also important to ensure that the broker is configured to use strong cipher suites. Cipher suites are algorithms that are used to encrypt data, and they vary in terms of strength. The stronger the cipher suite, the more secure the connection will be.

Some of the most popular cipher suites used with TLS include ECDHE-RSA-AES128-GCM-SHA256, DHE-RSA-AES128-GCM-SHA256, and RSA-AES128-GCM-SHA256.

Finally, it’s also a good idea to enable two-factor authentication (2FA) for additional security. 2FA adds an extra layer of protection by requiring users to provide two pieces of information before they’re able to access the system.

This could include something that the user knows, like a password, as well as something that the user has, like a physical token or a mobile phone. By requiring both, it makes it much more difficult for unauthorized users to gain access to the system.

2. Use a username and password

If an attacker were to gain access to your MQTT server, they would be able to view all of the messages being sent and received. This could include sensitive information such as passwords, credit card numbers, etc.

By using a username and password, you can restrict access to only those who have the correct credentials. This adds an extra layer of security and helps to ensure that only authorized users are able to view the data being transmitted.

3. Use an ACL file to control access

An ACL file is used to specify which users are allowed to connect to which topics. This means that you can control exactly who has access to which data, and you can be sure that only authorized users are able to receive or publish data to specific topics.

Without an ACL file in place, it would be possible for anyone to connect to your MQTT broker and subscribe to or publish data to any topic, which could potentially lead to sensitive data being leaked.

So, if you’re using MQTT, make sure you have an ACL file in place to help keep your data safe.

4. Use the most restrictive permissions possible

If an attacker were to gain access to your MQTT server, they would then have access to all of the data being transmitted through it. By using restrictive permissions, you can limit what an attacker can do if they do gain access to your server.

For example, you can restrict access to certain topics so that an attacker can only view data from those topics, and not other sensitive topics. You can also restrict access to publishing data to certain topics, so that an attacker can’t modify or delete data.

Restrictive permissions are a key part of security, and by using them you can help to protect your data.

5. Don’t use wildcards in topic names

When you use a wildcard in a topic name, you are essentially giving anyone who wants to publish to that topic the ability to do so. This could be a malicious actor trying to inject false data into your system or simply an authorized user who accidentally publishes to the wrong topic.

To avoid this, make sure that all of your topics are specific and do not use wildcards. If you need to allow multiple users to publish to a single topic, consider using a topic hierarchy with different levels of access. For example, you could have a “public” level where anyone can publish and a “private” level where only certain users have access.

6. Use unique client IDs

If an attacker knows the client ID of a device, they can impersonate that device and gain access to its data. By using unique client IDs, you make it much harder for attackers to guess the client ID of a device and impersonate it.

You should also use strong passwords for your MQTT broker. A strong password is one that is at least 8 characters long and contains a mix of uppercase and lowercase letters, numbers, and special characters.

7. Set up a bridge for remote connections

If you have devices that need to connect to an MQTT server over the internet, it’s not recommended to open up a port on your firewall and allow those devices to connect directly. Instead, it’s much more secure to set up a bridge.

A bridge is basically a middleman that sits between your devices and the MQTT server. Your devices connect to the bridge, and then the bridge connects to the server. This way, you don’t have to open up a port on your firewall, and your devices are still able to communicate with the server.

There are a few different ways to set up a bridge, but one of the most popular is using an SSH tunnel. With an SSH tunnel, you can encrypt all of the traffic between your devices and the server, so even if someone were to intercept the traffic, they wouldn’t be able to read it.

Setting up a bridge might sound like a lot of work, but it’s actually quite simple. And once you have it set up, you’ll be glad you did. It’s one of the best ways to secure your MQTT connection and keep your data safe.

8. Monitor your broker logs

Your broker logs contain a wealth of information about the health and status of your MQTT server. By monitoring these logs, you can quickly identify and resolve any issues that may arise. Additionally, broker logs can be used to track down malicious activity and investigate potential security breaches.

There are a few different ways to monitor your broker logs. One option is to use a third-party logging service, such as Loggly or Papertrail. These services provide an easy way to view and search your logs, and they offer additional features like alerts and notifications.

Alternatively, you can set up your own logging system using the open-source Graylog platform. Graylog is a powerful tool that offers a wide range of features, including the ability to tail log files in real-time.

No matter which method you choose, monitoring your broker logs is an essential part of keeping your MQTT server secure.

9. Keep MQTT brokers behind firewalls

An MQTT broker is a server that receives and processes messages from clients. Clients can be devices, applications, or other servers. By keeping brokers behind firewalls, you limit access to them and make it more difficult for unauthorized users to connect.

There are a few different ways to do this. One is to use a VPN. This will encrypt all traffic between the client and the broker, making it more difficult for someone to intercept and read messages.

Another option is to use SSH tunneling. This will also encrypt traffic, but it has the added benefit of providing authentication. This means that only clients with the correct credentials will be able to connect to the broker.

Finally, you can use TLS/SSL. This is similar to SSH tunneling, but it uses certificates instead of username and password authentication. This is generally considered to be the most secure option.

Whichever method you choose, the important thing is to make sure that only authorized users can access your MQTT brokers.

10. Consider using a VPN

When using MQTT, all communication is done over a broker. The broker is responsible for routing messages between clients and keeping track of which clients are subscribed to which topics. This means that the broker has access to all of the data being passed through it.

If you’re not using a VPN, then your broker is likely accessible over the internet. This means that anyone with the right skills could potentially eavesdrop on your communications or even tamper with the data being sent.

A VPN adds an extra layer of security by encrypting all traffic between the client and the broker. This makes it much more difficult for someone to snoop on the communication or tamper with the data.

There are many different VPN solutions available, so be sure to do some research to find one that’s right for you.