Firewalls

One of the main ways to control the information that goes in and out a network is the use of Firewalls. Usually a firewall is connected between the Internet and the local area Network, being it the only access to the network to Internet and viceversa. This way the information that goes in both ways can be controlled.

Nevertheless, even though that a network is protected by a Firewall, every computer behind it must be protected as well, due to hackers being able to avoid the firewall and access those computers.

Setting up a firewall is not always easy for inexperienced administrators creating confusing rules that can be used, or even show information to hackers about the type of firewall and the version that is it using; such information is used by hackers to get access to a firewall and take advantage of the vulnerabilities of the system.

On Linux there are several firewall, for example:


IP CHAINS, which has the following features:

  • Flexible manipulation of packages.
  • More complex counting.
  • Simple changes in policies.
  • It can block fragment specifically.
  • Suspicious packages registration.
  • It can manage other protocols besides ICMP/TCP/UDP.


NETFILTER

  • Allows to keep and inspect rules of packages filtering.
  • Provides package manipulation while they go through different parts of the kernel.
  • Masking support.
  • Standard packages filtering.
  • Translation of complete networks.


By: Carlos Castillo