Two-Factor Authentication for LINUX SSH

Before learning the two-factor authentication for Linux SSH, let’s have a small overview of Linux. Linux servers are one of the widest and most popular servers used by the organizations across the world. They constitute about 67% of all the public facing servers. They are one of the best and most efficient servers that can carry out the large volumes of web processes and transactions at a very low downtime.

Linux servers are highly reliable and scalable. They use SSH protocol to ensure secure login or access to remote servers. However, SSH involves the usage of the password, and a solely password-based authentication invites security threats and breaches. Passwords these days are no longer secure, for they can be hacked, cracked, or stolen using multiple methods.

Since Linux servers process large amounts of data that is mostly confidential, e.g. financial data, they are a large and favourable target to hackers and attackers. Protecting SSH logins merely with passwords may put your or an organization’s data at risk.

FairWare Ransomware targeting LINUX computers
FairWare Ransomware targeting LINUX computers

Click SSH security to read and learn more about the Linux SSH.

Why Two-Factor Authentication for LINUX SSH?

SSH or Secure Shell is a protocol that enables a user to log-in and access remotely located systems & servers securely, over an unsecured network. SSH itself not only encrypts the remote sessions but also delivers better authentication using cryptographic keys- a public key and private key.

As such, the combination of password and the cryptographic keys may seem to be a viable and stronger authentication option but it’s not, and the reason could be any of the following:

  • Cryptographic key (private key) may not be password protected and could be easily stolen.
  • Use of a simple password by the user in encrypting & protecting the private key.
  • System or device where the user has saved or stored the private key may be vulnerable to theft.

As discussed above, passwords are no longer effective to keep your servers protected from intrusion or other types of different security breaches. In addition, the introduction of concepts like BYOD (Bring Your Own Device) have brought more risk to the Linux servers by granting privilege to employees in accessing organization’s network, server and data using their personal devices like laptops, tablets and smartphones, which may be used as a gateway by attackers because of their comparably lower security levels in comparison to a server.

Two-Factor Authentication: Improving LINUX SSH security

Adopting and implementing two-factor authentication in Linux SSH enforces the server to double-check the authenticity of a user. With 2FA, user’s identity is verified and validated, using “what the user knows” and “what the user has”.

Two Factor Authentication for LINUX SSH
Two Factor Authentication for LINUX SSH

What does a user knows, is username and password.

What a user may have, is security token/code.

2FA places token-based authentication as a secure doorway between a user and the protected server. Anyone can knock on it but only the authorized user can open this door with a secret code.

Is it beneficial to secure all servers using 2FA?

Implementing 2FA protection has always proven to be beneficial irrespective of individual or organizational needs. 2FA may be implemented across all servers present within an organization, but that may create complexity in managing, accessing, and using those servers.

It is pertinent to mention that most servers are already protected and secured by the different types of versatile network security tools, such as firewalls and VPNs. However, all these network security methods may avoid and prevent intrusion only within the organization’s network boundaries.

Public-facing servers (usually very few) can be accessed and explored by any user remotely, over a maybe unsecured network, using SSH outside the organization’s secured network. As such these public-facing servers are most prone to intrusion & data-theft and require utmost protection. Thus, implementation of 2FA may be restricted to public facing servers only.

In conclusion, it may be stated that servers are meant for storing and executing large amount of business & organizational data. Therefore, expecting fullest protection of servers merely with a password is not less than a fool’s paradise. Two-factor authentication is one of the easiest and most convenient ways to ensure guaranteed and multi-layered protection to Linux servers.

Multi-Factor Authentication Vs Two-Factor Authentication

The present information technology era has been perceiving rising and severe cyber-attacks, especially security and data breaches. Weak and stolen credentials and passwords may be seen as one of the prime reasons behind most of the intrusions and data breaches. Thus, came the need for either replacing or making password-based authentication stronger and more reliable. In the world of web and computer security, we all must have heard the terms multi-factor authentication (MFA) and two-factor authentication (2FA) that are required to improve existing password-based security. However, most of the users find themselves confused over the differences between 2FA and MFA, like what’s the difference between them, which one to choose, and many similar types of queries.

What is Two-Factor Authentication or 2FA?

As the name suggests, two-factor authentication defines the mechanism for verifying and validating a user’s login credibility via two different authentication layers. The first layer of authentication involves user’s credential, i.e. username and password, verification. On successfully passing the password-based authentication, the user is directed to the second layer of authentication, where he/she needs to enter the security token to be authenticated. And finally, the authorized user gets the access.

2FA Working

Two-Factor authentication checks and validates the login based on following attributes:

Something a user knows: This may include registered credentials like username and password or pin. A user knowing correct or incorrect password may or may not get authenticated in the first security check, respectively.

Something a user has: This generally, refers to security codes or OTPs as hardware or software tokens, which are received or generated on their mobile or any other registered hardware devices. During this authentication, a user needs to provide the security token or code to verify his/her credibility in the final authentication check to gain access.

Learn some tips about 2FA in our blog- Tips for Using Two Factor Authentication Method.

What is Multi-Factor Authentication or MFA?

You may interpret the meaning of MFA through its name itself “multi-factor authentication”, i.e. authentication check involving multiple factors. In layman’s language, multi-factor authentication could be seen as the process of authenticating the user’s login veracity through multiple authentication layers, where each layer consists of different and unique parameters to verify and validate the user’s authenticity.

MFA working

In MFA, basically, a user is made to go through a defined sequence of authentication checks, starting from initial authentication check based on the password to more stringent authentications. These multiple and strict authentications comprise different factors to verify and validate the user’s identity.

  • Something user knows– password
  • Something user have– security tokens
  • Something user is– biometric scan
  • Location of the user– geographical location or coordinates
  • …….
  • …….
  • and so on

difference between mfa and 2fa

What’s the difference between MFA and 2FA?

The difference between MFA and 2FA is very minute in terms of authentication layers and factors used, which may be considered negligible. Basically, 2FA is a subset of MFA but vice-versa is not true. Authentications involving more than one authentication layers/parameters fall under the category of MFA. As such, 2FA, 3FA, 4FA,…… are nothing but the sub-categories of MFA.

In short, every 2FA is a multi-factor authentication, but all multi-factor authentications are not necessarily 2FA.

In the light of the above discussion, it may be stated that the selection between 2FA and MFA (2FA and above) should be based on the scope, boundary, data sensitivity, need of securing small, medium or large-sized infrastructure and many similar factors. It should be noted that more the authentication checks we have, better will be the security, but at the same time the user should not feel tiresome/difficult in getting authenticated.

2FA solutions like REVE Secure guarantees stronger and uncompromising security with their powerful two-factor authentication. Visit REVE Secure, to learn more.