Red Hat ENTERPRISE LINUX 3 - FOR X86-ITANIUMTM-AMD64 AND INTEL EXTENDED MEMORY 64 TECHNOLO, Installation Manual

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Chapter 4. Installing Red Hat Enterprise Linux 45
Enabling WWW (HTTP) does not open a port for HTTPS. To enable HTTPS, specify it in the
Other ports
field.
FTP
The FTP protocol is used to transfer files between machines on a network. If you plan on making
your FTP server publicly available, enable this option. You must install the
vsftpd
package for
this option to be useful.
SSH
S ecure SH ell (SSH) is a suite of tools for logging in to and executing commands on a remote
machine. If you plan to use SSH tools to access your machine through a firewall, enable this op-
tion. You need to have the
openssh-server
package installed in order to access your machine
remotely, using SSH tools.
Telnet
Telnet is a protocol for logging in to remote machines. Telnet communications are unencrypted
and provide no security from network snooping. Allowing incoming Telnet access is not recom-
mended. To allow inbound Telnet access, you must install the
telnet-server
package.
Mail (SMTP)
If you want to allow incoming mail delivery through your firewall, so that remote hosts can
connect directly to your machine to deliver mail, enable this option. You do not need to enable
this if you collect your mail from your ISP’s server using POP3 or IMAP, or if you use a tool such
as
fetchmail
. Note that an improperly configured SMTP server can allow remote machines to
use your server to send spam.
You can allow access to ports which are not listed here by listing them in the Other ports field. Use
the following format: port:protocol . For example, if you want to allow IMAP access through
your firewall, you can specify
imap:tcp
. You can also explicitly specify numeric ports; to allow
UDP packets on port 1234 through the firewall, enter 1234:udp . To specify multiple ports, separate
them with commas.
Finally, select any devices should allow access to your system for all traffic from that device.
Selecting any of these trusted devices excludes them from the firewall rules. For example, if you are
running a local network, but are connected to the Internet via a PPP dialup, you can check
eth0
and
any traffic coming from your local network is allowed. Selecting
eth0
as trusted means all traffic over
the Ethernet is allowed, but the ppp0 interface is still firewalled. If you want to restrict traffic on an
interface, leave it unchecked.
It is not recommended that you make any device that is connected to public networks, such as the
Internet, a trusted device.
Tip
To change your security level configuration after you have completed the installation, use the Security
Level Configuration Tool .
Type the
redhat-config-securitylevel
command in a shell prompt to launch the Security Level
Configuration Tool
. If you are not root, it prompts you for the root password to continue.