The name of this agency has changed several times, with ARPA being its initial name. In 1972, its name was changed to DARPA (to indicate a defense function). Then in 1993, the name was changed back to ARPA, and in 1996, it was changed once more to DARPA.
DARPA received funding to develop the ARPAnet—which evolved into the Internet—as well as funding to develop the University of California, Berkeley version of UNIX and TCP/IP. The mission of the Security and Intelligence Directorate (SID), a department within DARPA, in particular, is to provide credible security policy and procedures and to represent DARPA’s interests in National Security Forums.