# TCP Proxy (ISO8583) VGS TCP Proxy allows filtering out sensitive data with binary protocols. TCP stands for Transmission Control Protocol, a network protocol used for secure transfer of data over the internet. A common use case is transmitting data in the ISO8583 format, an international standard for financial transactions. This binary format can be processed via the VGS TCP Proxy. The proxy sits in front of incoming and outgoing TCP traffic and filters out sensitive data, such as the credit card number. Sensitive data is replaced in transit with [aliases](https://www.verygoodsecurity.com/blog/posts/tokenization-vs-encryption-vs-aliasing-how-to-truly-minimize-compliance/) supplied by VGS. VGS ensures that all the checksum data is updated properly after a TCP stream has been modified. For more details on the TCP Proxy, please contact us at --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.verygoodsecurity.com/vault/iso-proxy.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.