TOOLS FOR PROXYING

Tools for Proxying Many available applications provide proxy capabilities. The major commercial vendors have embraced hybrid technologies that combine proxy and stateful technologies, making it harder to identify when proxy techniques are used in their products. Mergers and acquisitions in the field have also added confusion to this subject For Example Gauntlet firewall. Gauntlet was one of the first, and most popular, proxy firewalls. Originally created by TIS, its technology was first acquired in 1998 by Network Associates, Inc (NAI). NAI continued to sell the products under the Gauntlet name. In 2002 though, NAI sold Gauntlet to Secure Computing, which already owned a competing firewall called Sidewinder. Secure Computing then integrated both products together to create a hybrid product

Firewall Toolkit (FWTK)  Firewall Toolkit was one of the first proxy firewalls. It was developed by Trusted Information Systems (TIS) under an Advanced Research Projects Agency (ARPA) grant.  It was first released in October of The key technology of FWTK was used to create the first version of the Gauntlet firewall. FWTK is still available at but has not been updated for many years.

Firewall Toolkit (FWTK)  FWTK is available in source code, which is an important part of its appeal. Anyone from a security analyst to a potential attacker can review its design to look for defects.  TIS referred to this as a crystal box design, a term coined by one of its first customers.  In a crystal box design, nothing about the design is hidden.  This same approach has been followed in the cryptographic community for decades. The belief is that if a design has not been peer-reviewed by the cryptographic community, no one should have any confidence in its security. product.

Squid  Squid is a highly regarded open source web proxy project. It provides high-performance proxy caching for HTTP, HTTPS, and FTP  Squid can be used in several web proxy scenarios. Its most frequent use is to cache browser requests for a site to accelerate and control web conversations. However, it is equally useful as a web server accelerator and as a reverse proxy server.

 Squid was designed to run under UNIX and has been successfully compiled on a broad set, including Linux, FreeBSD, OpenBSD, Mac OS/X, Sun Solaris, IBM AIX, and HP-UX. (Note that this is only a partial list.)  It can also be compiled to run under Windows if used in conjunction with the Cygwin ( and Mingw ( packages. Squid is available at

SOCKS  SOCKS is a proxy toolkit that enables applications to be proxied without requiring specific proxy code to be re-created for each client application.  The SOCKS server performs authentication and authorization functions on requests, establishes proxy connections, and relays data between hosts.  A SOCKS proxy server licensed for noncommercial use is available for free from

SOCKS  For applications to work with the SOCKS proxy server, they must be "SOCKS-ified." Most of the work involved in doing this has been packaged into the SOCKS software development kit (SDK).  SOCKS has evolved over time and gone through several revisions. SOCKS version 4 was the first popular version of SOCKS and is still in use.  SOCKS version 5 adds important features, including the support of UDP proxying as well as a variety of authentication methods.  The Internet Engineering Task Force (IETF) approved SOCKSv5 as the standard (RFC 1928) generic, proxy protocol for TCP/IP-based networking applications.

SOCKS VERSION 4  The SOCKSv4 protocol defines the message format and conventions to allow TCP-based application users transparent access across a firewall.  During proxy connection setup, the SOCKS server grants access based on TCP header information, including IP addresses and source and destination host port numbers.  The SOCKS server also authorizes users using Ident (RFC 1413) information.

SOCKS VERSION 5  The SOCKS version 5 protocol, also known as authenticated firewall traversal (AFT), is an open Internet standard (RFC 1928) for performing network proxies at the transport layer.  Following are the main added features in Proxy Version 5: 1.Strong Authentication 2.Address Resolution Proxy 3.Proxy for UDP-based Applications

SOCKS VERSION 5  There are two additional SOCKSv5-related standards to support authentication methods: 1. Username/password authentication for SOCKSv5 (RFC 1929) 2. GSS-API (Generic Security Service Application Programming Interface) authentication for SOCKSv5 (RFC 1961)