A keyboard led heartbeat program for linux which shows the load average as the flash frequency and with an integrated PS/2-keylogger detector:
Introduction to Basic Computer Security: A series of articles written by
Jennifer Vesperman that discuss the various aspects of computer security.
http://tldp.org/docs.html#intro
The (german) Live-CD Knoppicillin with the virus scanners BitDefender Antivirus
Scanner, F-Secure Anti-Virus and Sophos SAVScan with an online-update.
The virus
scanners do find also other malware than viruses and booting from
CD prevents counteractive measures from rootkits and other malware.
An alternative for the knoppicillin is the Ultimate Boot CD, also with 3 virus scanners.
Securing Debian Manual
Hardening a Linux or OpenBSD Installation
Security at Heise
Linux Security Howto
Linux Administrator's Security Guide
Deniable encryption e. g. with TrueCrypt or
the Encrypted Root File System Howto (Linux) or plus
steganography and data compression
with
steghide
Network Security Hacks (O'REILLY book)
Bruce Schneier (security technologist)
How to choose an easy to memorize and safe password (in
german), but i do recommend more than 10 characters for a password.
Anti-Spyware possibilities (directory loops, data hiding, etc.)
Physical IT Security with fire-, water- and bomb-safe 19"-racks (www.lampertz.de)
Common Criteria (CC)
Common Criteria (CC) at the BSI
IT-Grundschutz-Handbuch
(2006: 3612 Seiten dick)
Verschlüsselung / Kryptografie / Steganografie für Mail, Dateien,
Tauschbörsen / VoIP etc. (http://argh-it.de/crypto/)
Warnung vor den potenziellen Gefahren des Internet sowie
möglichen Maßnahmen für seine sichere Nutzung. Vom Landeskriminalamt Baden-Württemberg.
Unabhängiges Landeszentrum für Datenschutz Schleswig-Holstein
Sicherheit, Datenschutz, anonym surfen im Internet
http://www.bsi-fuer-buerger.de/
Onion Router like
TOR for countermeasuring Packet
sniffing, Traffic analysis and Telecommunications data retention.
Proxies like Squid and frox for Web caching, countermeasuring IP/OS/browser/referer etc. spying via http headers, and for proxy chaining. They can also be used for transparent proxying, e. g. for Onion Router exit nodes.
Freemailers with strong encryption for countermeasuring
email surveillance even without PGP/GPG
(see also http://www.gulli.com/netzwelt/ueberwachung/emailueberwachung/):
Hushmail (see
also http://www.gulli.com/news/hushmail-petzt-verschl-2007-11-08/ ).
Safe-Mail
And don't forget to use (free)mailers only via Anonymizers or Onion Routing and
neigther with your official IP nor your real data. If you need to fake data you
can use e. g. notwhoami or google and an webside imprint or a whois
output or ...
Security Tools, security lists and scanners at http://insecure.org/
Anti-Forensics:
Metasploit Anti-forensics homepage
http://www.ouah.org/p63-0x0b_Advanced_Antiforensics_and_SELF.txt
http://www.cio.com/article/print/114550
http://www.blackhat.com/presentations/bh-usa-05/bh-us-05-foster-liu-update.pdf
http://www.simson.net/clips/academic/2007.ICIW.AntiForensics.pdf
http://ws.hackaholic.org/slides/AntiForensics-CodeBreakers2006-Translation-To-English.pdf
Network Forensics Evasion: How to Exit the Matrix
A list of censorship-free DNS servers can be found e. g. at the CCC here for countermeasuring censorship via DNS.
echelonsig for countermeasuring Echelon and Carnivore (FBI).
Software anti-TEMPEST and the Complete, Unofficial TEMPEST Information Page.
See also Inside Echelon, Stasi 2.0 and decreasing the MTU for countermeasuring keyword based packet filtering or sniffing.