Big Brother is the simplest tool for monitoring your IP-network for troubles. It gives you a comprehensive picture of what happened to any point on the Net that you put in. Just add the host of interest by specifying its IP address or hostname and optional short description for your information.
Web Server Assessment Tool
Wikto is a tool that checks for flaws in webservers. It provides much the same functionality as Nikto but adds various interesting pieces of functionality, such as a Back-End miner and close Google integration. Wikto is written for the MS .NET environment and registration is required to download the binary and/or source code.
A generic IP network transaction auditing tool
Argus is a fixed-model Real Time Flow Monitor designed to track and report on the status and performance of all network transactions seen in a data network traffic stream. Argus provides a common data format for reporting flow metrics such as connectivity, capacity, demand, loss, delay, and jitter on a per transaction basis. The record format that Argus uses is flexible and extensible, supporting generic flow identifiers and metrics, as well as application/protocol specific information.
BASE is the Basic Analysis and Security Engine. It is based on the code from the Analysis Console for Intrusion Databases (ACID) project. This application provides a web front-end to query and analyze the alerts coming from a SNORT IDS system.
A general-purpose SSL cryptographic wrapper
The stunnel program is designed to work as an SSL encryption wrapper between remote client and local (inetd-startable) or remote server. It can be used to add SSL functionality to commonly used inetd daemons like POP2, POP3, and IMAP servers without any changes in the programs' code. It will negotiate an SSL connection using the OpenSSL or SSLeay libraries.
Brutus is one of the fastest, most flexible remote password crackers you can get your hands on - it's also free. It is available for Windows 9x, NT and 2000, there is no UN*X version available although it is a possibility at some point in the future. Brutus was first made publicly available in October 1998 and since that time there have been at least 70,000 downloads and over 175,000 visitors to this page. Development continues so new releases will be available in the near future. Brutus was written originally to help me check routers etc. for default and common passwords
HTTP Hacking
Spike Proxy is an open source HTTP proxy for finding security flaws in web sites. It is part of the Spike Application Testing Suite and supports automated SQL injection detection, web site crawling, login form brute forcing, overflow detection, and directory traversal detection.
Foundstone's enhanced netstat
Fport reports all open TCP/IP and UDP ports on the machine you run it on and shows what application opened each port. So it can be used to quickly identify unknown open ports and their associated applications. It only runs on Windows, but many UNIX systems now provided this information via netstat (try 'netstat -pan' on Linux). Here is a PDF-Format SANS article on using Fport and analyzing the results.
Tor is free software and an open network that helps you defend against a form of network surveillance that threatens personal freedom and privacy, confidential business activities and relationships, and state security known as traffic analysis.
Tor protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world: it prevents somebody watching your Internet connection from learning what sites you visit, and it prevents the sites you visit from learning your physical location. Tor works with many of your existing applications, including web browsers, instant messaging clients, remote login, and other applications based on the TCP protocol.
OSSEC is an Open Source Host-based Intrusion Detection System. It performs log analysis, file integrity checking, policy monitoring, rootkit detection, real-time alerting and active response.