TCP Wrapper

TCP Wrapper is a public domain computer program that provides firewall services for UNIX servers. The program was developed by Wietse Venema.

When an unprotected UNIX computer is connected to a network, the computer's system is exposed to other computer users connected to the network. For example, by using the finger utility, a hacker may be able to determine which users are logged on to a given server. It is also possible to find out the identities of individual computers, and various details about their users' recent Internet behavior. A hacker can determine when a workstation is likely to be idle, and then access and use that workstation when it is unattended. TCP Wrapper can act as a firewall to prevent this.

TCP Wrapper monitors incoming packets. If an external computer or host attempts to connect, TCP Wrapper checks to see if that external entity is authorized to connect. If it is authorized, then access is permitted; if not, access is denied. The program can be tailored to suit individual user or network needs.