Chapter 04

Chapter 04 - Linux Networking and Security Chapter 4 1...

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1 Linux Networking and Security Chapter 4
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2 Configuring Client Services Configure “superservers” to handle multiple network services Set up administrative services like logging and printing Use simple network information services like finger and talk Understand basic mailing list and news server configurations
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3 The Superservers Superservers listen on multiple network ports and start the appropriate service when a client connection arrives for that port. xinetd is a superserver gaining popularity It is a revised version of inetd that creates a more secure environment Shipped with Red Hat Linux xinetd is the most widely used superserver Application level security is provided via TCP Wrappers - the tcpd program
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4 TCP Wrappers
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5 TCP Wrappers TCP Wrappers - tcpd - is an application-level access control program TCP Wrappers is not a firewall and should be used with one if Linux security issues exist Configuration is done by two files: /etc/hosts.allow and /etc/hosts.deny Ensure proper and expected configuration by testing carefully before relying on it
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6 TCP Wrappers
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7 Services Beyond the Superserver Many services do not rely on superservers, they are designed to run standalone Apache Web server is the best example of this Servers such as SMTP and FTP can be used in standalone mode, or with inetd or xinetd FTP runs more efficiently in standalone mode if much FTP traffic is expected
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8 Exploring Network Testing Services There are 5 common testing services and they are used via Telnet The echo service repeats back whatever you type showing that a remote host is receiving typed data The chargen service returns a character stream and continues to until the session is ended The discard service is like /dev/null The time service returns a number corresponding to the current time and closes the connection The daytime service returns the current date/time in human- readable form, then ends the session
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9 Using Administrative Services Logging with logd System logging can be done remotely using syslogd by enabling another host to receive syslog messages across the network and specifying a host in /etc/syslog.conf Printing with lpd Linux can print across the network using lpd when printer definitions that specify remote hosts cause a local copy of lpd to contact lpd running on a remote host and forward the print job to that host
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10 Using Administrative Services
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11 Using Administrative Services
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Chapter 04 - Linux Networking and Security Chapter 4 1...

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