Cntlm is an NTLM/NTLMv2 authenticating HTTP proxy. It takes the address of your
proxy or proxies (host1..N and port1..N) and opens a listening socket,
forwarding each request to the parent proxy (moving in a circular list if the
active parent stops working). Along the way, a connection to the parent is
created anew and authenticated or, if available, previously cached connection
is reused to achieve higher efficiency and faster responses. When the chain is
set up, cntlm should be used as a proxy in your applications. Cntlm also
integrates transparent TCP/IP port forwarding (tunneling) through the parent
(incl. authentication).

WWW: http://cntlm.sourceforge.net/