Network Services access command line shell on local machine. connections can be authenticated to ensure remote system is the right one and not an imposter. command line required. telnet 23 Allows remote system to access command line shell on local machine. telnet-server Weak. User names and passwords sent in plain text. No. Use ssh instead. SMTP 25 Simple Mail Transfer Protocol. Used to transfer mail between systems. sendmail Weak. Mail tranferred in plain text. Only if mail needs to be handled locally. Encrypt sensitive mail before sending. time 37 Sends current time (in seconds since 00:00 1st Jan 1900) back to sender. xinetd None. No. Use NTP for time synchronisation. It is more accurate and has better security features. finger 79 Gives information about local system or users to remote machine. finger-server None. No. http 80 Web server. Httpd Depends on server configuration. Only if Web server needs to run on system. auth (ident) 113 Indentification protocol. Allows remote system to determine indentity of a user of a particular TCP/IP connection. pident Supports DES encryption of returned information. Only if needed to access some public services (e.g. some ftp sites and IRC). sftp 115 Secure File Tranfer Protocol. FTP-like data transfers over secure SSH connection. openssh Good. Only if file transfer required. nntp 119 Network News Transfer Protocol. Used to transfer USENET news groups. inn Depends on server configuration. Only if newsgroup server needs to be run on system. smb 137 138 Server Message Block. Allows Microsoft Windows Samba Weak. Information passed over network without encryption. Only use to access information that 416
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