introduction of iptables in linux

introduction of iptables in linux

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  By: Nouman Baloch
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  You Must Know Linux Kernel  Public and Private Network(LAN and WAN)  Ports  IP Addresses  MAC Addresses  Packets  DoS Attack
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  Topics  What isfirewall  What is iptables  Installing iptables  Targets And Jumps  Prevent DoS attack  Conclusion
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  What is Firewall A firewall is hardware, software, or a combination of both that is used to prevent unauthorized programs or Internet users from accessing a private network and/or a single computer. • A set of related programs that protects the resources of a private network from users from other networks.
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  What is iptable It is the modified firewall package available in linux operating system. Before it was known as ipchains, later it comes with some other improvements are:  Better integration with the Linux kernel, so improved speed and reliability.  Stateful packet inspection.  Filter packets according to TCP header and MAC address.  Better network address translation.  A rate limiting feature that helps iptables block some types of denial of service (DoS) attacks.
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  Installation of iptables In most Linux distros including Redhat / CentOS Linux installs iptables by default. You can use the following procedure to verify that iptables has been installed or not in Redhat. Open terminal and type the following command:  [root@localhost ~]# sudo info iptables  For the installation of iptables:  [root@localhost ~]# apt-get install iptables
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  Target and Jumps Each firewall rule inspects each IP packet and then tries to identify it as the target. Once a target is identified, the packet needs to jump over to it for further processing. -j - Jump to the specified target. By default, iptables allows four targets:  ACCEPT - Accept the packet and stop processing rules in this chain.  REJECT - Reject the packet and notify the sender that we did so, and stop processing rules in this chain.  DROP - Silently ignore the packet, and stop processing rules in this chain.  LOG - Log the packet, and continue processing more rules in this chain.
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  Preventing Dos Attack The following iptables rule will help you prevent the Denial of Service (DoS) attack on your webserver  # iptables -A INPUT -p tcp --dport 80 -m limit --limit 25/minute --limit-burst 100 -j ACCEPT  -m limit: This uses the limit iptables extension –limit 25/minute: This limits only maximum of 25 connection per minute.  –limit-burst 100: This value indicates that the limit/minute will be enforced only after the total number of connection have reached the limit-burst level.
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  Conclusion  We canget different service with this like firewall, routing, natting, logging and we can also block some types of DoS attacks just by implementing few rules in it.
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  FEEL FREE TO ASKANY QUESTION ?