Firewall security: Problems with simple Samba file share 3586

I have never set up any protective firewall. I have been on a T1 backbone for nigh on twenty years. I run slackware 3.0 (vintage 1996, I think). A quick nmap shows at least the following ports open:

PORT STATE SERVICE 7-tcp open echo 9-tcp open discard 11-tcp open systat 13-tcp open daytime 15-tcp open netstat 19-tcp open chargen 21-tcp open ftp 22-tcp open ssh 23-tcp open telnet 25-tcp open smtp 37-tcp open time 53-tcp open domain 79-tcp open finger 80-tcp open http 110-tcp open pop3 111-tcp open rpcbind 113-tcp open auth 139-tcp open netbios-ssn 143-tcp open imap 513-tcp open login 514-tcp open shell 587-tcp open submission 640-tcp open unknown 643-tcp open unknown 727-tcp open unknown 739-tcp open unknown 782-tcp open hp-managed-node 873-tcp open rsync 992-tcp open telnets 993-tcp open imaps 995-tcp open pop3s 1110-tcp open nfsd-status 1337-tcp open waste 2049-tcp open nfs 2401-tcp open cvspserver 6001-tcp open X11:1 6002-tcp open X11:2 7100-tcp open font-service 10000-tcp open snet-sensor-mgmt

and a few more that I would be forced to kill you if I told you about.

Peter