  Proxy servers are being increasingly deployed at organizations for
performance benefits; however, there still exists drawbacks in ease of client
authentication in interception proxy mode mainly for Open Source Proxy Servers.
  Technically, an interception mode is not designed for client authentication,
but implementation in certain organizations does require this feature. In this
paper, we focus on the World Wide Web, highlight the existing transparent proxy
authentication mechanisms, its drawbacks and propose an authentication scheme
for transparent proxy users by using external scripts based on the clients
Internet Protocol Address. This authentication mechanism has been implemented
and verified on Squid-one of the most widely used HTTP Open Source Proxy
Server.
