tcp wrappers For Linux

The tcp_wrappers package allows you to monitor and filter incoming requests for the SYSTAT, FINGER, FTP, TELNET, RLOGIN, RSH, EXEC, TFTP, TALK, and other network services. It provides tiny daemon wrapper programs that can be installed without any changes to existing software or to existing configuration files. The wrappers report the name of the client host and of the requested service. The wrappers do not exchange information with the client or server applications, so it does not impose no overhead on the actual conversation between the client and server applications.

It supports both 4.3BSD-style sockets and System V.4-style TLI. Praise yourself lucky if you don't know what that means.

The package provides tiny daemon wrapper programs that can be installed without any changes to existing software or to existing configuration files. The wrappers report the name of the client host and of the requested service; the wrappers do not exchange information with the client or server applications, and impose no overhead on the actual conversation between the client and server applications.

Optional features are: access control to restrict what systems can connect to what network daemons; client user name lookups with the RFC 931 etc. protocol; additional protection against hosts that pretend to have someone elses host name; additional protection against hosts that pretend to have someone elses host address.

The programs are very portable. Build procedures are provided for many common (and not so common) environments, and guidelines are provided in case your environment is not among them.

Requirements are that network daemons are spawned by a super server such as the inetd; a 4.3BSD-style socket programming interface and/or System V.4-style TLI programming interface; and the availability of a syslog(3) library and of a syslogd(8) daemon. The wrappers should run without modification on any system that satisfies these requirements. Workarounds have been implemented for several common bugs in systems software.

What to do if this is your first encounter with the wrapper programs: 1) read the tutorial sections for an introduction to the relevant concepts and terminology; 2) glance over the security feature sections in this document; 3) follow the installation instructions (easy or advanced). I recommend that you first use the default security feature settings. Run the wrappers for a few days to become familiar with their logs, before doing anything drastic such as cutting off access or installing booby traps.

What's New in This Release:

� Improved the anti source-routing protection. The code in version 7.5 was not as strong as it could be, because I tried to be compatible with Linux. That was a mistake. Sorry for the inconvenience. � � The program no longer terminates case of a source-routed connection, making the IP-spoofing code more usable for long-running daemons. � � When syslogging DNS hostname problems, always stop after a limited number of characters.