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I apologize for not being clearer. I am learning about firewall through linux SUSE. I am looking for information on how to edit the hosts.allow and the hosts.deny file and some examples. I have a linux box that I am practicing with to see how it works.
I am looking for information on how to edit the hosts.allow and the hosts.deny file and some examples. I have a linux box that I am practicing with to see how it works.
See 'man tcpd', but don't believe that this is the firewall.
'man iptables' would give you a decent introduction to the underlying 'iptables', but do note that SUSE (presumably openSUSE, not SLES/SLED) has its own firewall set-up system, within Yast. Now, this isn't normally a problem, as you just use Yast to set iptables up, but, if your objective is to get 'down and dirty' with the rules to understand iptables better, then it may not do what you want and it may get in the way, if you write your own iptables rulesets.
You might want to install the opensuse-security_en-pdf package which covers things like libwrap and suseFirewall2.
Look at chapter 14: Masquerading and Firewall.
Also read "man 5 hosts_access" and "man tcpd" for information about hosts_allow and hosts_deny. Some services such as smbd (samba) let you configure access in their own config files as well.
SuSE's firewall also has a config file /etc/sysconfig/SuSEfirewall2 as well as scripts for each service in /etc/sysconfig/SuSEfirewall2.d/. Using openSuSE, you configure items in /etc/sysconfiig/SuSEfirewall2 by setting variables. E.G.
FW_SERVICES_DMZ_UDP="". When the firewall service starts, it sources the config files and uses the variables to create the iptables commands that are run.
You can still modify rules using the iptables command in your learning process. For example, suppose someone is banging on port 22.
Add your own rule, dropping packets coming from that IP address. Then check /var/log/messages to verify that the attack has stopped.
Also check out the System Administrators Guide (SAG guide). Install the "books" package, or download from the tldp.org website.
hosts.allow and hosts.deny are for tcp wrappers which is a separate security mechanism than iptables. There are multiple ways of doing security for different things. For hosts.allow and hosts.deny to work for a given application it must be tcp wrapper aware.