sbd is a Netcat-clone, designed to be portable and offer strong encryption. It runs on Unix-like operating systems and on Microsoft Win32. sbd features AES-CBC-128 + HMAC-SHA1 encryption (by Christophe Devine), program execution (-e option), choosing source port, continuous reconnection with delay, and some other nice features. sbd supports TCP/IP communication only.
Unix-privesc-checker is a script that runs on Unix systems (tested on Solaris 9, HPUX 11, Various Linuxes, FreeBSD 6.2). It tries to find misconfigurations that could allow local unprivileged users to escalate privileges to other users or to access local apps (e.g. databases).
CryptCat is a simple Unix utility which reads and writes data across network connections, using TCP or UDP protocol while encrypting the data being transmitted. It is designed to be a reliable “back-end” tool that can be used directly or easily driven by other programs and scripts.