Wireless network connection validating identity firewalled
Nmap is the network and service scanning tool of choice for most security professionals.
It is a free, open source application available on all UNIX and Windows operating systems.
Fyodor, the author of NMAP, has conducted a yearly survey of the members of his mailing list (over 4,000 high-energy security professionals) to rank the top 100 security tools.
This list includes a number of the tools discussed in this section.
If you execute Nmap with its default settings, and assuming you have root privileges, Nmap performs a SYN scan: Nmap sends a SYN to all of the ports listed in its services file (over 1,000 ports) and looks for a SYN/ACK response.
Because UDP doesn't have a handshake process like TCP, the UDP packet must be crafted in a manner that causes the operating system to respond back.If you send a UDP packet to a closed port on a server, the TCP/IP stack is supposed to send an ICMP port unreachable message back.If a host does not send this response, it is assumed that the port is open.Security testing as a process is covered, but the focus is on gathering the evidence useful for an audit.One thing is certain about security auditing tools: The power and sophistication of tools that auditors have at their disposal increase exponentially every year.
There are also a number of free whitepapers and guides on the Internet.