Multi-Factor Authentication (MFA) (sometimes referred to as Two Factor Authentication or 2FA) provides an additional layer of security on top of your username and password. It is powerful because even if an attacker manages to hack, guess, or steal your password they won't be able to get into your account.

This article includes guidance on How to turn on MFA; What Type of MFA System to Use; and Where to Get MFA Apps:

Wherever possible, turn on MFA for your online accounts. How to do this varies between accounts but will usually be found in the Password or Security section of Settings or your Profile. For example:

There are several different types of MFA: text-based; app-based; hardware key; and more:

Ark Light recommends that you use an app on your phone for MFA as the best balance between security and convenience. This means that when you log in you will need to enter a short code generated by the app. This is a secure system because it can't be spoofed by an attacker and is protected by the encryption and login security of your phone. There are several good applications, including:

A hardware key is a physical device that you plug into your computer's USB port when prompted during the login process. For example, Yubico's products here. This is a very secure system but you do need to physically have the key with you, which may be inconvenient. You may also find that a single key doesn't work for all your devices: laptop, desktop, and phone.

This is probably the most common form of MFA and it's a reasonable choice. However, there are ways for attackers to fraudulently gain access to SMS messages sent to your phone, often called 'SIM-swap fraud' or 'SIM hijacking' - see this article from Verizon for more information. Therefore, Ark Light recommends that you use SMS-based MFA only if App-based is not available.