The Berkeley Internet Name Domain (BIND) implements an Internet name server for Unix operating systems. The BIND consists of a server (or `daemon') called `named' and a resolver library. A name server is a network service that enables clients to name resources or objects and share this information with other objects in the network.
CustomDNS is a modular DNS server written in Java. It's based on Brian Wellington's dnsjava pacakge, but it adds support for virtual hostnames, SQL databases, and dynamic client updates. You can use CustomDNS out-of-the-box as a clone of ml.org/dyndns.org, or you can use it to develop custom DNS applications.
djbdns is a collection of Domain Name System tools. Security is one of the primary motivations for the development of djbdns. Every step of the design and implementation has been carefully evaluated from a security perspective. The djbdns package has been structured to minimize the complexity of security-critical code. dnscache is immune to cache poisoning. It is advisable to use the package as a secure alternative to BIND.
dnsjava is an implementation of the DNS protocol in Java. It supports all of the common record types. dnsjava provides both high and low level access to the resolver. The high level functions perform queries for records of a given name, type, and class, and return an array of records. A cache is used to reduce the number of queries sent. The low level functions allow direct manipulation of dns messages and records, as well as allowing additional resolver properties to be set. A 'dig' clone, dynamic update program, and basic server are also included. Extensions to the DNS protocol are supported as well (DNSSEC, TSIG, EDNS0).
pdnsd is a Proxy DNS server for Linux and FreeBSD that is designed to cope with unreacheable nameservers (e.g. because the dial-in link is not up) in a graceful manner to prevent DNS-dependent applications like Netscape from hanging. It has a permanent disk cache (i.e. the cache contents are saved in a file on exit) and supports parallel query and a wide variety of link uptests. It also has the ability to serve some types of locally defined records.
TrinityOS is a step-by-step, example-driven HOWTO on building a very functional Linux box with strong security in mind. TrinityOS is well known for its strong packet firewall ruleset, Chrooted and Split DNS (v9 and v8), secured Sendmail (8.x), Linux PPTP, Serial consoles and Reverse TELNET, DHCPd, SSHd, UPSes, system performance tuning, the automated TrinityOS-Security implementation scripts, and much more.
Arb-Scan is a remote banner scanner written in bash and Perl. It supports 12 different services banner checks (daytime, ftpd, sshd, smtpd, domain, finger, httpd, pop2, pop3, nntp, imapd and snpp). It features IP file reading, logging, random IP scanning, ftp anonymous login checking and VRFY/EXPN smtp checking.