SSH
The Secure Shell under Linux and VNUML.
Download (german)
Related Slides (german)
Netfilter / IPTables
Netfilter is the basis for IP filtering and manipulation under Linux (since Kernel 2.4). So it is on the bottom of firewalls and NAT.
Honeypot
"Honeypots" are set up as a trap to analyze attacks from hackers: One computer, that is obviously completely unsecured, is integrated into a network to be a worthwhile target for an attack. The attacker can now be observed by special tools. With VNUML you don't need to set up a real physical computer as a honeypot but you can use a virtual machine in a secure virtual environment .
