Definition
Multi-factor authentication, or MFA, is a security process that verifies a user's identity using two or more distinct pieces of evidence. These factors typically fall into three categories: something the user knows (like a password), something the user possesses (like a phone or hardware token), and something the user is (like a fingerprint or facial scan). When logging in, a user must provide credentials from at least two of these categories to gain access. Implementing MFA significantly strengthens security by making it much harder for unauthorized individuals to access accounts, even if they steal a password. For instance, a bank might require both your password and a one-time code sent to your mobile phone to log into your account. This is distinct from two-factor authentication (2FA), which specifically uses exactly two factors, whereas MFA can encompass three or more. MFA is a critical concept tested on certifications like CompTIA Security+ and CISSP, and is fundamental to secure cloud environments.