jlip is a SLIP-driver with additional features like one logical link over many physical lines (multiline), IP-over-TCP tunnelling with public key hosts authorization (elliptic curves) and data encryption (blowfish with 112-448 bits key) for VPNs (Virtual Private Networks). It currently works under FreeBSD only and there are no english docs. A russian to english translation is welcome.
VTun is the easiest way to create Virtual Tunnels over TCP/IP networks with traffic shaping, compression, and encryption. It is a user space implementation and doesn't need modification of any kernel parts. VTun supports IP, PPP, SLIP, Ethernet, and other tunnel types. VTun is easily and highly configurable; it can be used for various network tasks like VPN, Mobil IP, Shaped Internet access, Ethernet tunnel, IP address saving, etc.
AMaViS (A Mail Virus Scanner) scans e-mail attachments for viruses using third-party virus scanners available for UNIX environments. It resides on a UNIX (Linux) machine and looks through the attached files arriving via e-mail, generates reports when a virus is found and sets the delivery on hold.
COSA and SRP are synchronous serial boards for ISA bus which have two channels. Each channel can be set up to one of the X.21, V.24, V.35 and V.36 hardware interfaces. The Linux kernel driver and user-space tools serve for setting up and using the COSA and SRP boards under Linux. It allows you to use it with the following link-level protocols: Cisco HDLC , synchronous PPP, or as the frame-based character device.