Foundstone’s free security downloads

http://www.foundstone.com/us/resources-free-tools.asp
Free tools for security concerns from a division of McAfee. From the site:
As the premier provider of security risk management, vulnerability assessments and protection, Foundstone has created a series of tools that are used in the field by its consultants. The company offers this software free of charge to the public. Download them today to [...]

Internet Storm Center

http://isc.sans.org/
From the site:
The ISC was created in 2001 following the successful detection, analysis, and widespread warning of the Li0n worm. Today, the ISC provides a free analysis and warning service to thousands of Internet users and organizations, and is actively working with Internet Service Providers to fight back against the most malicious attackers.

DiamondCS

http://www.diamondcs.com.au/index.php
Like the site says, security software for Windows systems. Stumbled across them (no, not using SU) a decade ago looking for tiny apps specializing in specific security features, and these guys provided. The apps are small and very well developed.

Nirsoft.net

http://www.nirsoft.net/
NirSoft is the website of Nir Sofer, who has written a number of small, free windows utilities. These applications are useful tools that run on Windows up to and including XP, for the most part.

WireShark

http://www.wireshark.org/
From the website:
Wireshark is an award-winning network protocol analyzer developed by an international team of networking experts.
Runs on OS X, Linux, Solaris, and Windows. Also, see the wiki for more information here:
http://wiki.wireshark.org/

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