[ Thanks to Zinoune for this link. ]
“1. Nmap: The Network Mapper is an open source tool to exploit
security auditing. Though it was made to quickly scan big networks,
it works fine on single hosts as well. This tool makes use of raw
IP packets using new ways to find the hosts that are present on the
network, the services they are offering, OS they are running,
packet types in use, and other characteristics. Nmap runs on many
types of computer systems, and comes in both graphical and console
versions.“2. Nikto: It is a GPL server scanner that performs
all-inclusive tests for web servers using many parameters,
including thousands of possibly dangerous CGIs/files, and problems
related to specific versions on hundreds of servers. Plugins and
scan data is updated regularly.”