ippacket
Generates IP/TCP/UDP/ICMP packets, with a curses interface

ipsend
Generates TCP/IP packets with a scripting language (Darren Reed)

SPAK
Module generates TCP/IP packets by a shell pipe (IP, TCP, UDP) ( Karyl F. Stein)

TOD
Touch of Death. Is able to kill connections, if used with sniffit ( Brecht Claerhout )

udpprobe
Send and receive UDP Packets

Network Scanning and Diag

nmap
good Port scanning tool which supports all well-known methods. On the namp Page is a link list of other scanning tools, too.

netdiag
Collection of Diagnosis Tools: strobe, tcpspray, trafshow, statnet, netwatch, tcpblast and netload. Source can be found on all Debian Mirrors in source/net/netdiag*.tar.gz

netcat
from Hobbit - Swiss Army Knife for TCP and UDP (like socket). Simple Port Scanner, simple Port redirector and simple access to sockets from Scripts.

iptraf
LAN statistic utility for Linux

btng
Beholder, The Next Generation RMON compliant Ethernet monitor

Trinux
A Linux Security Toolkit. Boot-Disks with some Scan/Sniff Tools

smb-nat
SMB Network Analysis Tool (1.0 and 2.0beta)

ADMsmb
ADM smb is a security scanner for Samba/LAN Manager Server Message Blocks/Window Shares from the ADM CreW

PortScanner
a simple TCP Portscanner

DOSTracker
MCI's DOSTracker can recognize and trace quite a few Deny-Of-Service Attacks on CISCO Networks back to the entry point of the attack.

queso
Queso identifies operating systems via the TCP packet signature

SmbScanner
SMB (Windows Share) Scanner by !Hispahack

traffic-vis
can visualize amount of traffic on IP networks between hosts

Host security Scanners

satan
Scanner with Web Frontend from Dan Farmer and Wietse Venema (look at his papers and tools)

Nessus
a security Scanner for Linux, *BSD*, Solaris and NT with different Frontends like Java and GTK

gate
Modular Linux Scanner Uses a user-friendly Curses GUI

saint
scanner based on Satan (not realy free)

COPS
a Un*x host security tool from Dan Farmer

Tiger
'tiger' is a set of scripts from TAMU that scan a Un*x system looking for security problems, in the same fashion as Dan Farmer's COPS.

Dumping and Sniffing

Hunt
The main goal of the HUNT project is to develop a tool for exploiting well known weaknesses in the TCP/IP protocol suite. It implements some "new" features which apparently are not available in any other free product.

tcpdump
Uses libcap to capture network packets

sniffit
Packet Sniffer (Brecht Claerhout)

epan
offline protocol analyser for tcpdump ([html] Peter Tobias)

tcpshow
reformats tcpdump output ([mail] Mike Ryan)

ITA
List of software in the Internet Traffic Archive, used to analyse, simulate and anonymize traffic

Argus
CMUs Network Monitoring Tool. Note: Argus 1.7 is ported to a lot of architectures, but it is not Free anymore.

karpski
A Gtk based sniffer with a nice GUI, well suited for ARP monitoring

ethereal
it's a utility that lets you capture and analyze network traffic. Based on GTK.

IPAC
IP Accounting Frontend to ipfwadm

netlog
TAMUs network logging toolkit [dir] including logging monitors for UDP and TCP, an extractor, and [txt] netwatch a real time network monitor

KSniff
KSniff is a packet sniffer/analyzer developed for the KDE project which supports plugins written in TCL.

netwatch
Netwatch allows a user to monitor an Ethernet segment or PPP line and examine activity on the network.

TODO:

ipgrab

icmpinfo

ESniff

net-acct

arpwatch

getethers

trafshow

ip daemons

IP Filter, NAT, VPN, IP encryption

CIPE
Crypted IP Encapsulation (Daemon and Module for Linux). Very lightweight secure VPN Solution by Olaf Titz

IP Filter
(TCP/IP Packet Filtering package for *BSD* based Systems and Linux including NAT, transparent Proxies and statefull screening.

masq/masqd
for Linux and winmasq
the win32 frontend from Jaume Miralles.

ipfwadm paper
about Linux build in packet filter by Jos Vos.

ipchains
the new Linux IP Filter

The Linux FreeS/Wan Project
with IPSEC, ISAKMP/Oakley and DNSSEC

sf firewall
dynamic statefull packet filter for Linux.

Linux IP-NAT Forum
real RFC NAT with Linux 2.0 from Michael Hasenstein

VPN for OpenBSD
in the current-tree of OpenBSD you can find a IPsec implementation and a photurisd key management daemon. This is documented in [html] vpn(8).

ppptcp
Tunnel PPP over an arbitrary TCP connection

PPP on top of SSH
simple scripts to build a VPN based on SSH

drawbridge
TAMU's Filtering Bridge, a firewall Solution. Old Versions where running on DOS, the current version [dir] is running on FreeBSD.

VPS
Virtual Private Server for building VPNs based on PPP-over-SSH

Crypto+Privacy

GnuPG
The GNU Privacy Guard, a free PGP (2.6, 5.x, OpenPGP)

psst
... A free Shecure Shell Implementation

CTC
is a freeware PGP-interoperable encryption software package (including a PGP lib and a Mac Client)

SSLapps FAQ
about aaplications based on SSLeay

SRP Telnet and FTP
Secure Remote Password Project

Nautilus
Secure voice conversation

PGPPhone
Freeware Voice-over-IP Solution for Win32 with PGP security

Cryptonite
pure Java package for strong encryption

gPGPshell
gtk-interface to PGP and GnuPG

Superservers and TCP Wrappers

xinetd
xinetd is a replacement for inetd, the internet services daemon

UCSPI tcpserver

tcpcontrol

TCP Wrapper

g2s
An interesting inetd replacement including tcpwrapper/chrootuid/relay

tcp_server
small and simple tcp server

API-level Emulators and Proxies

API-level Emulators and Proxies

usocksd
User-Mode Socks5 Daemon

SOCKS 4+5, ssocksd

term

slirp

Port Forwarders

rinetd
redirects multiple tcp connections to remote hosts (behind the firewall) from Thomas Boutell at Boutell.Com, Inc

redir
simple TCP Port redirector

netcat
See describtion in Section Network Scanning

socket
The program implements access to TCP sockets from shell level.

plugdaemon
Daemon to redirect connections, with some support for load balancing from Peter da Silva

uredir
simple udp redirector

Mail

IspMailGate
a general-purpose email filter integrated into sendmail, written in Perl and based on the MIME-tools. (not realy free)

smtpd/smtpfwd
Free Store+Forward SMTP Relay with Header-Filtering

Secure Tunnels

ssh (not realy free)

sslwrap
inetd redirector for SSL to unsecure services like POP3 or HTTP

stunnel
SSL wrapper like sslwrap can run from inetd or standalone, can wrap remote services

HTTP (and CONNECT for SSL)

Web-Servers which are able to act as an HTTP Proxy: Apache
, W3C httpd (CERN)
, Jigsaw (the W3C's Java Server)
, Roxen
. (See the Section in Yahoo!)

WebFilter
is a extension to the CERN Proxy for Content Filtering (like Advertising)

Squid
powerfull Internet Object Cache

WWWOffle
Proxy optimized for Offline Browsing

The Internet Junkbuster
standalone Proxy which can filter Content from Web Pages

Muffin
HTTP (SSL connect) Proxy written in Java with Filter capability

RabbIt
filtering Web-Proxy in Java, especially for slow lines, can produce lowres images on the fly

tinyproxy
small proxy for http. Does not cache and can be run in anon mode

NNTP (News)

Acme.Nnrpd
multithreaded Java NNTP Proxy

Misc Protocols

ByPRoxy
A personal Proxy for Filtering Internet Access (HTTP, SMTP, POP3, NNTP) (not realy free)

tircproxy
A Proxy for IRC (Internet Relay Chat) featuring DCC support by Bjarni Einarsson

DeleGate
Proxy/Cache/conversion/server for multiple protocols (FTP, HTTP, NNTP, ...) runs on different platforms

xgate
allows X11 connections through one-way firewalls like socks.

FreeTDS
free implementation of Microsofts and SyBase' TDS (Tabular DataStream) database client access protocol

bnc
a simple irc bouncing (proxy) tool

xtacas
an extended Version of Cisco's TACAS Server by Vikas Aggarwal

Cistron RADIUS server
by Miquel van Smoorenburg

Mig's RADIUS LAbs
some summaries on the Linux-radius list

Lucent RADIUS
RADIUS Whitepaper, FAQ and Server

RADIUS Services for NDS
Novell offers this for free download

Basic Merit AAA Server
The Server formerly known as Merit Radius Server

LDAP at U-M
free Server and Clients for LDAP and X.500

Linux directory services
integrating LDAP into Linux (as a replacement for NIS)

Innosoft's LDAP World Implementation Survey
including free implementations

GAP
the General Authentication Protocol by Olaf Titz.

ident2
rewrite if an identd/auth protocol server

OpenLDAP
LDAP Tools based on the UMich's LDAP

Simple Distributed DataBase (SDDB)
a system designed to hold network directory type information across multiple machines. It is designed to be an intranet level service rather than in an internet level one. It allows updates to occur in multiple places (seperated by WAN links) and yet the data to be merged into one seamless directory.

Intrusion detection

Integrity Checking

Tripwire


NCSfck
file integrity checker (like tripwire)

Nannie
It monitors system files for change in inode, size, etc. and notifies you if a change occurs.

Attack Detection

Gabriel


tocsin


courtney


Abacus Sentry
Detects TCP and UDP Port scaning, including stealth scans (not realy free)

gxsnmp
the GNOME Network Management Application. On this page you find some good links to SNMP Solutions

Scotty and Tkined
TKined is small and nice network management station based on Scotty which extends TCL with interesting network capabilkities.

Hummingbird Project
distributed data collecting with Postgres SQL backend

Pong3
system management tool

ucd-snmp
SNMP suit from the UC Davis, including support for Linux ipfwadm

psntools
managing a great number of user accounts at a site

PIKT
monitors systems, reports problems, and fixes those problems automatically whenever possible

cheops
GTK network shell which maps hosts and offers tools to work on them, uses portscanner and queries OStype

Log Analysis

swatch

Logcheck
Fast and Reliable Log File Auditing (not realy free)

wots
WOTS is a logfile monitoring utility written in perl5. It's based on swatch but is brand new.

squij
analyse squid logfiles for refresh pattern setting

logscanner
a logscanner which can perform realtime notifications

Firewall Configuration and Adminstration UI

FCT
Fireall Configuration tool can generate ipfwadm and IPFilter Rules

ipfwadm dotfile module
makes setting up of ipfwadm files for simple installations easy. John Hardin wrote that module for Jesper Pedersen's [html] Dotfile Generator.

Mason
shellscript which generates ipfwadm rules by sniffing actual traffic patterns ([mail] William Stearns)

DNi
IP Filtering Firewall script for dial-up users based on javascript for Linux' ipfwadm

Fake
relace existing systems with backup servers (hot spare backup systems)

Operating Systems (Kernel, Patches, Extensions, Hardening)

Linux

FreeBSD

OpenBSD
pretty secure OS

NetBSD

Rule Set Based Access Control for Linux

Titan
is a collection of programs, each of which either fixes or tightens one or more potential security problems with a particular aspect in the setup or configuration of a Solaris/Unix system. Conceived and created by Brad Powell, it was written in Bourne shell, and its simple modular design makes it trivial for anyone who can write a shell script or program to add to it, as well completely understand the internal workings of the system.

Unsorted

Trinoo
Diverse stuff related to DDoS (Distributed Denial of Services). Docs and tools can be found here.

Freestone from SOS Corporation
Patches for Security Tools from SOS.

Juniper Firewall Toolkit from Obtuse Systems Corporation
Freier Store und Forward SMTPd
Utilities Sammlung from Obtuse.

The Firewall Toolkit from TIS

FWTK FAQ
A lot of information and the Patches for transparent support

qmail newer, faster and more secure Mail Transfer Agent.

RIGAT
Remote Integrated Graphical Administration Tools.

BlackMail SPAM Protection
[email protected]

JNet