CIFS (common Internet file system) is a protocol that lets programs make requests for files and services on remote computers across the Internet. Developed by Microsoft®, CIFS is a public or open variation of the older SMB protocol. It uses the client/server programming model.

These file-sharing protocols were originally designed for wired network connections, so they require a large number of request/response transactions and their performance degrades significantly over high-latency WAN links such as the Internet.