echo and chargen (TCP and UDP Ports 7 and 19)systat (TCP Port 11)FTP: File Transfer Protocol (TCP Ports 20 and 21)Anonymous FTPFTP active modeFTP passive modeSetting up an FTP serverRestricting FTP with the standard Berkeley FTP serverSetting up anonymous FTP with the standard Unix FTP serverAllowing only FTP accessSSH: The Secure Shell (TCP Port 22)Host authentication with SSHClient authentication with SSHTelnet (TCP Port 23)SMTP: Simple Mail Transfer Protocol (TCP Port 25)Configuration filesSecurity concerns with SMTP banners and commandsSMTP relaying and bulk email (a.k.a. spam)Overflowing system mailboxesDelivery to programsOverall security of Berkeley sendmail versus other MTAsTACACS and TACACS+ (UDP Port 49)Domain Name System (DNS) (TCP and UDP Port 53)DNS zone transfersDNS nameserver attacksDNSSECDNS best practicesBOOTP: Bootstrap Protocol, and DHCP: Dynamic Host Configuration Protocol (UDP Ports 67 and 68)TFTP: Trivial File Transfer Protocol (UDP Port 69)finger (TCP Port 79)The .plan and .project filesDisabling fingerHTTP, HTTPS: HyperText Transfer Protocol (TCP Ports 80, 443)POP, POPS: Post Office Protocol, and IMAP, IMAPS: Internet Message Access Protocol (TCP Ports 109, 110, 143, 993, 995)Sun RPC’s portmapper (UDP and TCP Ports 111)Identification Protocol (TCP Port 113)NNTP: Network News Transport Protocol (TCP Port 119)NTP: Network Time Protocol (UDP Port 123)Sudden changes in timeAn NTP exampleSNMP: Simple Network Management Protocol (UDP Ports 161 and 162)rexec (TCP Port 512)rlogin and rsh (TCP Ports 513 and 514)Trusted hosts and usersSpecifying trusted hosts with /etc/hosts.equiv and ~/.rhosts/etc/hosts.lpd fileRIP Routed: Routing Internet Protocol (UDP Port 520)The X Window System (TCP Ports 6000-6063)/etc/logindevpermX securityThe xhost facilityUsing Xauthority magic cookiesTunneling X with SSHRPC rpc.rexd (TCP Port 512)Communicating with MUDs, Internet Relay Chat (IRC), and Instant Messaging