RC4 is a stream cipher, a type of encryption algorithm designed to secure digital data by scrambling it into an unreadable format during transmission. Developed in 1987 by Ron Rivest, RC4 was widely used in protocols like SSL/TLS and WEP for wireless networks. However, over time, significant vulnerabilities were discovered in RC4, making it susceptible to various attacks that can compromise encrypted information. As a result, RC4 is now considered insecure and is no longer recommended for protecting sensitive data. Modern encryption standards have replaced RC4 in most applications to ensure stronger security.