DES, or Data Encryption Standard, is a symmetric-key algorithm used for encrypting digital data. It was developed in the early 1970s and became a federal standard in the United States in 1977. DES uses a fixed-size key of 56 bits to transform plaintext into ciphertext, making it difficult for unauthorized users to access the original information. Despite its widespread use, DES has become less secure over time due to advances in computing power. In the late 1990s, it was deemed vulnerable to brute-force attacks, leading to the development of stronger encryption methods, such as AES (Advanced Encryption Standard), which replaced DES as the standard for secure data encryption.