Third, you learn a lot with starting to program, just porting programs. Nmap is a portscanner for linux, you can use about 7 methods of scanning as well as the few stealth methods known. On our homepage there are two useful products we wrote for a school project. Fast and reliable. You have to be administrator to install the packet driver which comes with it.
Sources are also available.
They are both written in CBuilder. The source of the sniffer will be soon online. The scanner source is already online. I haven't seen any reference to these, so I decided to send an email about them to those who don't know what they are. DOS, or denial of service, are usually commands or shell scripts that are not hard to make or do and are used in a malicious manner.