TrinityOS is a step-by-step, example-driven HOWTO on building a very functional Linux box with strong security in mind. TrinityOS is well known for its strong packet firewall ruleset, Chrooted and Split DNS (v9 and v8), secured Sendmail (8.x), Linux PPTP, Serial consoles and Reverse TELNET, DHCPd, SSHd, UPSes, system performance tuning, the automated TrinityOS-Security implementation scripts, and much more.
SSHTerm is a fully-featured Java SSH terminal that provides a whole range of features including port forwarding, password and public-key authentication, full clipboard support, record and playback input/output, and the ability to load/save connection settings to a file. The SSH terminal is now seamlessly integrated with a secure VNC viewer, a port forwarding manager, and a full SFTP client.
rrs is a reverse (connecting) remote shell. Instead of listening, it will connect out to rrs in listen mode. The listener will accept the connection and receive a shell from the remote host. rrs features full pseudo-TTY support, full OpenSSL support (client/server authentication and choice of cipher suites), Twofish encryption, a simple XOR cipher, plain-text sessions, peer-side session snooping, a daemon option, and reconnection features. It is known to compile and run under Linux, FreeBSD, NetBSD, OpenBSD, and QNX.
alph implements and analyzes historical and traditional ciphers and codes, such as polyalphabetic, substitutional, and mixed employing human-reconstructable algorithms. It provides a pipe filter interface in order to encrypt and decrypt block text to achieve transparency. The program is meant to be used in conjunction with external programs that transfer data, resulting in transparent encryption or decryption of information. The program can thus be used as a mail filter, IRC filter, IM filter, and so on.
Secure Back Door (SBD) is a tool that provides ultra-secure and minimal access to a computer, which allows you to run a single command based on a one time key. It is good if you don't want to have an SSH server running all the time, and only want to start it when needed. Because it is written in only a few lines of code, it is hoped that it will be less susceptible to security exploits than a program like SSH.
ansistego provides terminal-level steganography for scripts and other ASCII files (ie, protection against 'cat'). It intersperses a text/script with commented ANSI codes that cause most terminals to clear sensitive lines as soon as they are written. Only a specified front text appears. The front text is embedded in the script using ANSI-cloaked comments, so that the text appears unaltered when the script is viewed with cat, but the script can be run without any decoding stage.