Differential Fault Analysis (DFA) is a cryptographic attack technique used to exploit vulnerabilities in block ciphers. It involves introducing faults into the encryption process and analyzing the differences between the faulty and correct outputs. By carefully observing these differences, attackers can deduce information about the secret key used in the encryption. This method is particularly effective against certain algorithms, as it can reveal weaknesses in their design. DFA typically requires access to the encryption device and the ability to induce faults, making it a practical threat in scenarios where physical access is possible.