i have setup a three computer network at home..all three machines run both windows98 and red hat linux7.1 ...just out of curiosity i downloaded a port scanner (nmap ) and ran a scan on one of the windows machine...and i did get a list of ports...
port 23
port 21 (i had installed a telnet and ftp server for windows)
port 139
and a few other port numbers
all these port have their repectives daemons listening for a connection i suppose...and all of them needs passwords....
i was wondering how a hacker who attacks a remote site with out any knowledge of the system users or passwords use a portscanner to get the port list and then gain access by attacking these ports??
on my windows machine i can never get the command prompt when i telnet from the linux machine using an invalid password..(well! that is obvious)...so how are these informations of listening ports useful to a hacker,if he has no pass or at the least a valid account in the machine....