Some SSH Security Tips

Photo via ChrisDag

To begin, we will start with a brief explanation of what SSH is and how it operates. SSH, also known as Secure Shell is a network protocol for use between two computers that allows for data to be communicated in a secure manner, the ability to command execution, and a variety of other functions. Although it is used to execute commands into remote machines, it also works with other connections such as tunneling and X11. It is mostly used with Unix or Unix-like systems, and serves as a more reliable replacement for outdated shell protocol systems such as Telnet.

SSH has the ability to transfer files using either SCP or SFTP protocols, and runs based on a client-server model. For key management purposes, SSH supports authentication systems that use passwords that encrypt through keys which are generated automatically. It also keeps a record of all keys used from the remote side, and password authentication has the ability to be turned off. For Unix systems, all authorized keys get stored in the home folder of the remote user.

The more you learn about how SSH works, the better equipped you will be to use it to effectively ward off all of the various forms of hacking attacks that exist in this day and age. Hackers are always coming out with new ideas, so it’s impossible to give an extensive list of precautions. However, the following list of security tips is a good place to get started.

1. Use Software to Stop Brute Force Threats

Brute force attacks are one of the most archaic forms of hacking attempts, but they can still wreak plenty of havoc on your system if you are not adequately prepared for them. Many hackers use this method because, in theory, it can crack almost any system when given enough time. Using a simple yet effective brute-force search scheme, hackers have the ability to go into your server and decrypt your key. If they accomplish this, you could be in for all sorts of headaches, depending on what the hacker’s purposes are and how ruthless they decide that they want to be.

Thankfully, however, there are a number of measures that you can take to minimize the effect of brute force threats, and effectively make it so that getting into your server is simply not worth the hacker’s time. You can acquire programs that make it possible to obfuscate your data. Although data obfuscation does not actually prevent hackers from being able to crack your server’s code, it makes the data much more difficult to understand once it has been cracked. There are also programs that impose a limit on the number of times a password can be attempted. The most common of these types of programs is CAPTCHA, a challenge-response test that most people who use the internet regularly have encountered at one point or another.

2. Put Users in Chroot Jail

Chroot is basically an operation pertaining to Unix and Unix-like systems that causes the apparent root directory of the process that is currently running, as well as each of its child processes (a “child process” is the term for a process that is created through a separate process). As the system admin, you are given the capabilities of altering the system’s environment into a “chroot jail”, which is created when you modify the environment to a point where a program cannot name any of the files that are located outside of the designated directory tree. As a result, the program is also unable to access the files altogether.

3. Implement the Timeout Interval

One particularly important and useful feature in SSH is the ability for the system admin to implement a timeout interval for all users. A timeout interval has the function of automatically logging out users at a specific preset time interval. Often times, many users will forget to log out, and thus create a vulnerability to their system. Others may purposely choose to stay logged in at all times, being either unaware of the potential threats they face or simply not caring. Regardless of what the case may be on your server, a timeout interval can help to remedy all of these situations.