WS-Security is a standard that provides a way to secure web services by ensuring the confidentiality, integrity, and authenticity of messages exchanged between parties. It defines how to attach security tokens, such as XML Signature and XML Encryption, to messages, allowing for secure communication over the internet. This standard is part of the broader Web Services framework and is often used in conjunction with other specifications like SOAP and WSDL. By implementing WS-Security, organizations can protect sensitive data and ensure that only authorized users can access their web services.