Mason  
   Tool that interactively builds a firewall using ipfwadm, ipchains, or netfilter/iptables firewalling. [GPL]
   http://mason.stearns.org/

ipgrab  
   A packet sniffing tool, based on the Berkeley packet capture library; that prints complete data-link, network, and transport layer header information for all packets it sees.
   http://ipgrab.sourceforge.net/

ippl - IP Protocols Logger  
   Performs logging of incoming IP packets by utilizing a multi-threaded approach. Administrators can perform filtering of captured packets.
   http://pltplp.net/ippl/

ADMsmb  
   A network scanner that detects Microsoft Windows shares using the SMB protocol.
   ftp://ADM.isp.at/ADM/ADMsmb-v0.2.tgz

Cheops  
   Cheops is a complex network utility integration tool that offers network topographic visualization.
   http://www.marko.net/cheops/

Argus  
   A generic IP network transaction auditing tool that performs network monitoring.
   http://ciac.llnl.gov/ciac/ToolsUnixNetMon.html#Argus

Arping  
   A set of network diagnostic tools, such as an enhanced replacement for traceroute.
   ftp://ftp.inr.ac.ru/ip-routing/iputils-current.tar.gz

Bsign  
   Offers file integrity verification via digital fingerprints.
   ftp://ftp.buivi.com/pub/bsign/

CIPE  
   A Crypto IP Encapsulation project. Offers a protocol that passes encrypted packets between prearranged routers in the form of UDP packets.
   http://sites.inka.de/sites/bigred/devel/cipe.html

CTC  
   Freeware PGP, Pretty Good Privacy interoperable encryption software package. CTC is Rot13 for PGP.
   http://www.bifroest.demon.co.uk/ctc/

Dante  
   A circuit-level firewall and proxy that can be used to provide convenient and secure network connectivity to a wide range of hosts. Very similar to a SOCKS implementation.
   http://www.inet.no/dante/

Hummer- from the Hummingbird Project  
   Hummer is a complex tool that lets you distribute security and intrusion detection information between several hosts. Therefore, it can be used to detect sophisticated attacks where multiple attackers and targets are mixed and matched.
   http://www.csds.uidaho.edu/~hummer/

Hping  
   A network scanner that uses spoofed source address packets.
   http://www.kyuzz.org/antirez/hping.html

FreeTDS  
   Free Tabular DataStream package. Tabular DataStream is a client-to-database server protocol in SyBase and Microsoft SQL database implementations.
   http://www.freetds.org/

DeleGate  
   An application-level gateway server.
   http://www.delegate.org/delegate/

Deception Toolkit  
   Performs emulation of other operating systems and vulnerabilities not found on the host; in order to deceive and solicit invaild attempts of exploitation by malicious individuals.
   http://all.net/dtk/download.html

Cistron RADIUS Server  
   An authentication and accounting server for terminal servers that speak the RADIUS protocol.
   http://www.radius.cistron.nl/

DNI  
   Adds the ability for a network administrator to set packet filtering rules via a web page interface. unsecure from an external source, but very easy to use for intranet management.
   http://members.tripod.com/~robel/dni/dniadm.html

DrawBridge  
   A BSD-based firewall with source included. This binaries main value is that it is perfect for beginners learning how firewalls are developed.
   http://drawbridge.tamu.edu/

FirePlug EDGE Router Project  
   Suite aimed at turning a minimally configured consumer PC into a standalone internet firewall; complete with address translation, proxying, and IP packet forwarding.
   http://edge.fireplug.net

EPAN - Ethernet Protocol Analyzer  
   A protocol analyzer that supports ethernet, Token Ring, SLIP, PPP, ISDN, and loopback.
   http://www.et-inf.fho-emden.de/~tobias/epan/

dnswalk  
   A tool for automatically debugging databases by performing a zone transfer of a current zone. Inspects individual records for inconsistencies, and generates warnings or errors where appropriate.
   http://www.visi.com/~barr/dnswalk/

Ethereal Network Analyzer  
   Network protocol analyzer for Unix that allows examination of data from a live network, or from a capture file on disk.
   http://www.ethereal.com

FAKE: IP Address Takeover Tool  
   Allows you to take over the IP address of another machine in your LAN via ARP spoofing.
   http://www.ca.us.vergenet.net/linux/fake/

Gnusniff  
   Datagram sniffer for the Linux operating system.
   http://members.ozemail.com.au/~peterhawkins/gnusniff.html

icmpquery  
   icmpquery is a tool for sending and receiving ICMP queries for the destinations address mask and current time.
   http://www.angio.net/security/

JunkBuster  
   Freeware for Unix/Linux/FreeBSD/OS2/BeOS/Windows 95/98/ME/NT4. Web proxy that filters banner ads, cookies, and referer tracking. Supports wafers and User-Agent spoofing.
   http://internet.junkbuster.com/

IP Filter - TCP/IP Packet Filtering package  
   An advanced TCP/IP packet filter suitable for use in firewall environments. Can be loaded as a module or compiled into the kernel.
   http://cheops.anu.edu.au/~avalon/ip-filter.html

ipfwadm Dotfile Module  
   Helps inexperienced Linux network administrators perform IP masquerading and firewalling on a small network easier.
   http://www.wolfenet.com/~jhardin/ipfwadm.html

Isinglass  
   Consists of tools to create a firewall for dialup machines.
   http://www.tummy.com/isinglass/

Fenris  
   A suite of tools intended to simplify reverse engineering, black-box security audits, computer forensics and vulnerability testing.
   http://razor.bindview.com/tools/fenris/

Central Command - Vexira Antivirus Solutions  
   Vexira Antivirus for Linux workstations and servers. A complete virus defense system designed for easy and dependable virus prevention on Linux systems.
   http://www.centralcommand.com

GNUPG- Gnu Privacy Guard  
   An open source OpenPGP compatible encryption system. Provides data integrity services for messages and data files by using digital signatures, encryption, and compression.
   http://www.gnupg.org/

IPTraf  
   IPTraf is a console-based network statistics utility that gathers TCP connection paket and byte counts, interface statistics, and activity indicators. Also captures all TCP/UDP packets.
   http://iptraf.seul.org/

Stadrin  
   Strong user authentication and access control for Linux environments in a fully integrated system using PAM modules.
   http://www.stadrin.com

Hacking Linux  
   The ultimate resource for securing your linux workstation/server.
   http://www.hackinglinux.co.uk

Linux-PAM  
   Linux Pluggable Authentication Modules (PAM) is a flexible mechanism for authenticating users using alternative authentication schemes.
   http://kernel.secsup.org/linux/libs/pam/

COLD  
   Protocol LAN analyzer that can monitor various interfaces: ISDN, PPP, Token Ring, standard: loopback, 10baseT Ethernet.
   http://www.ipv4.it/cold/

COPS  
   The famed Computer Oracle and Password System is a suite of tools that can automatically detect configuration problems or holes in your system.
   http://www.trouble.org/cops/

Etherboot  
   Free software package for booting x86 PCs over networks.
   http://etherboot.org/

BitDefender Linux Edition v.7.0 (for Workstations)  
   Free effective anti-virus security solution for systems running Linux; free updates of all signature files and high scanning speed.
   http://www.bitdefender.com/

Razorback  
   A log analysis program that interfaces with the SNORT open source Intrusion Detection System to provide real time visual notification when an intrusion signature has been detected on the network.
   http://www.intersectalliance.com/projects/RazorBack/