Active port scanning

It can be interesting to see which internet services a range of machines provide (it's often possible to find interesting information about a system by accessing those services using telnet)

Before you can scan for open ports you must select Edit → Options... → Advanced then select Enable active probing

Select Tools → Scan Addresses...

Enter the range of addresses you want to probe, and select the services you want to look for

• Reverse DNS - this isn't a service, instead selecting this box attempts to lookup the hostname of each IP address scanned
• Mail - port 25, SMTP mail
• Usenet - port 119, usenet news
• Web - port 80, http web service
• Telnet - port 23, remote login
• Nameserver - port 42, nameserver

If you want to scan a wider selection of ports hit the Advanced>> button and select ports in the scrollable list

Note scanning a lot of ports seems to put a lot of stress on the windows sockets library. Strange bugs and crashes happen with some versions of winsock