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Linux Netfilter Tutorials

Tutorials, howtos and tips about Linux netfilter/iptables firewall includes examples, configurations, blocking traffic and IP address, opening and closing ports, and much more. ( rss feed )

Ubuntu Linux Save / Restore Iptables Rules

I want to make changes to an iptables configuration. How to do I Save and Restore an iptables Configuration in Ubuntu Linux server?
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Linux Iptables Just Block By Country

I admin ecom website and a lot of bogus traffic comes from countries that do not offer much in commercial value. How do I just configure Apache or iptables to just refuse connections to certain countries?
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Q. How do I detect port scan attacks by analyzing Debian Linux firewall log files and block port scans in real time? How do I detect suspicious network traffic under Linux?
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Q.Can you explain the meaning of following two firewall rules present in my /etc/sysconfig/iptables rules under CentOS Enterprise Linux version 5.2?

-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
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Q. I've CentOS Linux server configured with APF firewall. How do I open port 22 from specific IP address only? I've fix static ADSL IP address assgined and I'd like to open port 22 from my IP 202.5.1.3 only using APF firewall script. How do I configure firewall?
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Q. I've only one public IP address assigned by my ISP using metro Ethernet connection. eth0 has public IP and eth1 is connected to our network switch. How do I configure Linux box to forward traffic to my web server hosted at 192.168.1.100 IP address?
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Q. I've Linux box acting as software router (natted) for over 100 computer connected via LAN. Regular netstat command is not displaying the list of all natted connections. How do I find out connections managed by netfilter / iptables which comes with the Debian 4.x system?
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