Tag Archives: firewall

Linux iptables Firewall Simplified Examples

In the previous post, we’ve talked about how to Secure Linux Server Using Hardening Best Practices and some people ask me about firewall section which was a brief introduction about iptables firewall. Today we will discuss in detail the Linux iptables firewall and how to secure our servers traffic using that awesome tool.

Source: Linux iptables Firewall Simplified Examples – Like Geeks

25 Useful IPtable Firewall Rules Every Linux Administrator Should Know

In this article, we will show you some 25 useful iptable firewall rules that will help you to manage and control you Linux firewall through iptables easily.

Source: 25 Useful IPtable Firewall Rules Every Linux Administrator Should Know (Tecmint)

Install And Configure Arno Iptables On Ubuntu 14.04

Today, we will come to know how we can install and configure arno iptables on Ubuntu 14.04 LTS. This is related to security hardening of your server. A good System Administrator must secure his Linux driven servers. There are many ways we can secure our servers. Setting up a good solid firewall is an essential step to take in securing any modern operating system according to your needs. I will show you how to install & Configure arno iptables On Ubuntu 14.04 LTS for securing your servers.

Source: Install And Configure Arno Iptables On Ubuntu 14.04 (Unixmen)

How to set up an alternate SIP port (other than 5060) using Webmin

One problem that some VoIP users are experiencing these days is that they have trouble connecting to their home Asterisk, FreeSWITCH, YATE, or other software PBX server, but only when using certain ISP’s.  One suspicion is that certain ISP’s that offer their own VoIP or traditional landline service attempt to mess with packets using the common SIP port 5060, hoping customers will think that VoIP is unreliable and will subscribe to the company’s overpriced offering instead (see this thread at BroadbandReports.com).

There are various ways to enable an alternate SIP port on the server (in addition to the usual port 5060) but if you are using Webmin to manage your firewall, here’s an easy way, in just three steps:

Step 1:

If you use Webmin to manage your firewall, then you already know how to get to the Linux Firewall page.  So go there and select the Network Address Translation (nat) table in the dropdown at the top of the page.  Then when the page changes, click the topmost Add Rule button (in the Packets before routing (PREROUTING) section):

SIP Port Forwarding 1

Step 2:

Now you should see this page. The items you need to change are indicated by the red ovals.  The Destination TCP or UDP port is set to 7654 in this example, but don’t use that.  Pick your own unique port; just make sure that it’s not used by anything else on the server already.  And yes, you really do put the alternate SIP port you want to use in the Destination setting; it may not make intuitive sense but that’s just how it is.  Avoid using ports in the range 10000 through 20000 because those are used for RTP traffic, and avoid ports below 1024 because those are protected ports that are reserved by the system.  There are also other ports you should avoid (those used by other software on your system) but if you don’t know how to find ports in use on your system, a bit of time with a search engine will lead you to several pages that show you how to detect already active ports.  It can vary a bit depending on your operating system, and it’s beyond the scope of this article.

SIP traffic is UDP only, not TCP (there may be rare exceptions but most software PBX’s use UDP by default).  If by some very odd chance you are using TCP for SIP traffic (why?!?) then you will need to specify that under the Network Protocol item.  Also, note that the incoming interface is set to eth0 in this example – Webmin will usually show the correct one by default, but you want to select the interface used by incoming SIP traffic if you happen to have more than one.  Don’t forget to click Save when you’re finished.

SIP Port Forwarding 2

Step 3:

After you have saved the page you should be back at the page you came from, and it should now show your new forwarding rule.  If it does, just click Apply Configuration at the bottom of the page to make it active:

SIP Port Forwarding 3One other thing you might need to to is add a rule on the main Linux Firewall page allowing incoming traffic on your selected alternate port, if you have a restrictive firewall that blocks most traffic by default.  Try it first without doing that, but if your clients can’t connect on the alternate port, just be aware that you may need to do that before they will be able to connect.  For more security, you can enable access to your SIP ports only from specific IP addresses, if your remote clients are at fixed IP addresses.

Now you should be able to change the port number on your SIP endpoints from the default 5060 to your alternate port.  Of course I can’t guarantee it will always work, but if you try it and suddenly find that your SIP connections become far more reliable, you might want to leave a comment, and mention the ISP that you suspect might be messing with SIP traffic.

By the way, if you are NOT using Webmin to manage your firewall, and have iptables installed, then all you should need to do is enter these two lines from a command prompt (replace 7654 with your chosen alternate port).  But I strongly caution you NOT to do this if you are using Webmin to manage your firewall:

iptables -t nat -A PREROUTING -i eth0 -p udp --dport 7654 -j REDIRECT --to-ports 5060
/etc/init.d/iptables save

Link: How to Create Advanced Firewall Rules Using Windows Firewall

Firewall is an important and necessary tool to protect us from the unsecure Internet. Most of the modern OSes come with a built-in firewall, but the problem is that few people know of its existence and only a few know how to configure it.

Windows is no different. By default, it comes with a decent built-in firewall which is capable of controlling all the incoming and outgoing traffic. This built-in Windows firewall is a bit clunky with a not-so-friendly user interface and complex rules, though it does gives you plenty of control on overall rules like blocking, restricting, whitelisting, etc. In this article, we are going to show you how to create advanced firewall rules in Windows firewall to block an application from accessing the Internet.

Full article here:
How to Create Advanced Firewall Rules Using Windows Firewall (Make Tech Easier)

Link: The Beginner’s Guide to iptables, the Linux Firewall

Iptables is an extremely flexible firewall utility built for Linux operating systems. Whether you’re a novice Linux geek or a system administrator, there’s probably some way that iptables can be a great use to you. Read on as we show you how to configure the most versatile Linux firewall.

Full article here:
The Beginner’s Guide to iptables, the Linux Firewall (How-To Geek)

Link: Managing the Iptables Firewall

Your firewall is an important first line of defense on any publicly-accessible server. In previousarticles I listed how to set up a firewall without getting into any detail. This article goes into depth with configuring your iptables firewall.

Full article here:
Managing the Iptables Firewall (Fideloper)

Link: How to Install and Configure UFW – An Un-complicated FireWall in Debian/Ubuntu

The ufw (Uncomplicated Firewall) is an frontend for most widely used iptables firewall and it is well comfortable for host-based firewalls. ufw gives a framework for managing netfilter, as well as provides a command-line interface for controlling the firewall. It provides user friendly and easy to use interface for Linux newbies who are not much familiar with firewall concepts.

While, on the other side same complicated commands helps administrators it set complicated rules using command line interface. The ufw is an upstream for other distributions such as Debian, Ubuntu and Linux Mint.

Full article here:
How to Install and Configure UFW – An Un-complicated FireWall in Debian/Ubuntu (TecMint)

Link: How to protect Apache with Fail2ban

Around 2 years ago I wrote an article about fail2ban.

Fail2ban is an intrusion prevention framework written in the Python programming language. It is able to run on POSIX systems that have an interface to a packet-control system or firewall installed locally (such as, iptables or TCP Wrapper).

Fail2ban’s main function is to block selected IP addresses that may belong to hosts that are trying to breach the system’s security. It determines the hosts to be blocked by monitoring log files (e.g. /var/log/pwdfail, /var/log/auth.log, etc.) and bans any host IP that makes too many login attempts or performs any other unwanted action within a time frame defined by the administrator.

Today I want to show you some configurations that you can use to improve the security of your Apache.

Read the rest here:
How to protect Apache with Fail2ban (Linuxaria)