Search Results for: firewall

How to secure Linux System With TCP Wrappers

The TCP Wrappers package is installed by default on Fedora Linux and provides host-based security separate from that provided by a firewall running on the server itself or elsewhere. The application relies on two main files: /etc/hosts.allow: Defines the hosts and networks allowed to connect to the server. The TCP Wrappers enabled application searches this(…)

How to Use a Non-Standard Port for SSH

By default, ssh listens for incoming connections on port 22. For a hacker to determine ssh is running on your machine, he’ll most likely scan port 22 to determine this. An effective method is to run ssh on a non-standard port. Any unused port will do, although one above 1024 is preferable. Many people choose(…)

How to configure single IP Addresses in IPtables

Opening up a whole interface to incoming packets may not be restrictive enough and you may want more control as to what to allow and what to reject. Lets suppose we have a small network of computers that use the 192.168.0.x private subnet. We can open up our firewall to incoming packets from a single(…)

How to configure to allow Interfaces in IPtables

You would like to block all network traffic using iptables firewall under Debian GNU/Linux. This will block all incoming and outgoing traffic including Internet aka ADSL/ppp0 and it is highly recommend. The logic is block everything and allow only required traffic. This can be done with four simple commands: # iptable -F # iptables -P(…)

A brief to various iptables commands

We will use an example based approach to examine the various iptables commands. In this first example, we will create a very simple set of rules to set up a Stateful Packet Inspection (SPI) firewall that will allow all outgoing connections but block all unwanted incoming connections:

How to Install and Configure iptables under CentOS

Working with iptables from the command line requires root privileges, so you will need to become root for most things we will be doing. Iptables should be installed by default on all CentOS 3.x, 4.x and 5.x installations. You can check to see if iptables is installed on your system by: $ rpm -q iptables(…)

How to Install and Configure Sendmail on Solaris

Sendmail is one of the oldest and mostly widely used MTAs in the world. It is the default MTA for most UNIX distributions, including HP’s HP-UX, IBM’s AIX, and Sun Microsystems’ Solaris OS. Sendmail’s long life has made it complicated to configure and maintain, but it makes up for its drawbacks with its ability to(…)

How to Build a diskette-based bandwidth management system – PicoBSD

Many users, despite having a good Net connection, complain about poor surfing and download speeds. While an organization could pay for additional bandwidth, a better option might be to manage the bandwidth they already have. There are numerous bandwidth management software tools available. In this article we will explore managing network bandwidth using the dummynet(…)

How do I configure IPSec without encryption

Phase 1 must be encrypted, but phase 2 may be configured without encryption. VPN 3000 Concentrator Navigate to Configuration > Policy Management > Traffic Management > SAs. Click Add to add a new security association (SA). For the encryption algorithm, select null and configure the remaining settings for this SA. Apply the new SA to(…)