|By Joshua Drake||
|September 20, 2001 12:00 AM EDT||
(LinuxWorld) -- As I write this column, the world suffers infestation by yet another Internet worm, and again the worms are intended to attack Microsoft-based machines. Fortunately for my company, we don't run any Microsoft-based machines, but the Nimda worm still affects us.
Nimda eats our bandwidth since other companies sharing our subnet are running infectious Windows 98, NT, and 2000 machines. These diseased, ill-maintained beasts from the land of insufficient light are now trying to infest our stable, secure, long running, easy-to-use, well-behaved Linux machines. (Can you tell I'm a bit irritated?)
This has led me to start editing some of our firewall rules, and in the process, consider that, as we have recently migrated to the 2.4 kernel, some people may be interested in how to create a Linux 2.4 kernel-based firewall quickly.
The following examples do not create the perfect firewall. What I describe is designed to give a system administrator a little piece of mind by fortifying a machine from obvious attacks.
The 2.2 version of the Linux kernel used the ipchains application to control the firewall. For standard firewalling, ipchains is a decent solution. We still use it on some of our machines, and there is still a positive argument for 2.2 kernel-based firewalls, because the 2.4 kernel still has some stability issues under heavy load.
Those heavy load issues aside, the 2.4 kernel provides a wealth of networking capabilities 2.2 lacks. These include stateful firewalling and solid quality-of-service options. One could argue that the 2.4 kernel, and its iptables firewall code, enables a person to build intricate firewalls capable of competing with the likes of CheckPoint.
The command to execute iptables is simple: as root type
iptables. The execution of the previous command should display output similar to the following:
[root@jd root]# /sbin/iptables iptables v1.2.1: no command specified Try `iptables -h' or 'iptables --help' for more information. [root@jd root]#
If you would like an output of the available options when using the iptables you can pass the
-h flag during program execution. The
-h command will result in output similar to the following:
[root@jd root]# /sbin/iptables -h iptables v1.2.1 Usage: iptables -[ADC] chain rule-specification [options] iptables -[RI] chain rulenum rule-specification [options] iptables -D chain rulenum [options] iptables -[LFZ] [chain] [options] iptables -[NX] chain iptables -E old-chain-name new-chain-name iptables -P chain target [options] iptables -h (print this help information)
Commands: Either long or short options are allowed. --append -A chain Append to chain --delete -D chain Delete matching rule from chain --delete -D chain rulenum [...]
For this article, I am not going to go into exhaustive explanation of all the iptables options. If you want an advanced introduction, to iptables I suggest the Linux 2.4 Packet Filtering HOWTO (see resources below).
When developing a personal or desktop firewall I practice a very simple philosophy. If you aren't going to use it, don't open it. For example, if you are not hosting a Web site, do not open port 80. If you are not using telnet (and there is not a good reason on this Earth to use telnet), do not open port 23!
In an effort to follow my philosophy, the quickest way to port protection nirvana is the following iptables chain:
/sbin/iptables -A INPUT -p tcp --syn -j DROP
The previous statement will allow you to, as the user of the computer, performed all your normal Internet activities. You will be able to browse the Web, ssh out, or chat with a colleague on ICQ. On the other hand, the outside world, when trying to connect to your Linux box via TCP/IP, will simply be ignored. This is a reasonable solution for most Linux computers.
However, one of the benefits of Linux is its remote management capabilities. One of the more popular ways that people remotely manage Linux machines is via the SSH (see resources) suite. SSH typically operates on port 22 and thus, we would need to enable connections to port 22, while keeping the rest of the connections closed. This can be done with the following iptable chains:
/sbin/iptables -A INPUT -p tcp --syn --destination-port 22 -j ACCEPT /sbin/iptables -A INPUT -p tcp --syn -j DROP
It is probably not a good idea to let the world connect to your machine on port 22 unless you run a public server. Therefore, we can limit which machines can connect to port 22 by modifying the iptable chain, and adding the
-s option. The
-s in this example specifies what source address is allowed to connect to the server.
/sbin/iptables -A INPUT -p tcp --syn -s 192.168.1.110/32 --destination-port 22 -j ACCEPT /sbin/iptables -A INPUT -p tcp --syn -j DROP
The addition of the
-s 192.168.1.110/32 will enable only the remote machine with the IP address of 192.168.1.110 to connect to your protected host.
When you create an iptables-based firewall, each chain (for simplicity's sake, each line) will be read sequentially. Thus, it is possible to have the previous configuration of only one machine having rights to connect via SSH, and to run a public Web server. This could be done with the following commands:
/sbin/iptables -A INPUT -p tcp --syn -s 192.168.1.110/32 --destination-port 22 -j ACCEPT /sbin/iptables -A INPUT -p tcp --syn --destination-port 80 -j ACCEPT /sbin/iptables -A INPUT -p tcp --syn -j DROP
This is just an introduction to iptables, but it does give a reasonable representation of the bare essentials for a firewall. If you are currently running Linux with kernel 2.4, it may be a good time to review what your firewall looks like. On a closing note, if you are still running kernel 2.2 and you are looking for a good firewall configuration utility, take a look at Guard Dog (see resources).
|Peter 10/04/04 12:38:21 PM EDT|
Thank you... this is the info I have been looking for, a quick and simple way to secure a basic web server.
|Jules 07/24/04 02:19:10 PM EDT|
Thankyou! At last an article that shows me how to create a simple set of rules.
|Pankaj Kumar 09/27/03 12:17:26 AM EDT|
Good introductory article on iptables for newbies.
The buzz continues for cloud, data analytics and the Internet of Things (IoT) and their collective impact across all industries. But a new conversation is emerging - how do companies use industry disruption and technology enablers to lead in markets undergoing change, uncertainty and ambiguity? Organizations of all sizes need to evolve and transform, often under massive pressure, as industry lines blur and merge and traditional business models are assaulted and turned upside down. In this new data-driven world, marketplaces reign supreme while interoperability, APIs and applications deliver un...
Oct. 9, 2015 08:00 AM EDT Reads: 285
Too often with compelling new technologies market participants become overly enamored with that attractiveness of the technology and neglect underlying business drivers. This tendency, what some call the “newest shiny object syndrome,” is understandable given that virtually all of us are heavily engaged in technology. But it is also mistaken. Without concrete business cases driving its deployment, IoT, like many other technologies before it, will fade into obscurity.
Oct. 9, 2015 08:00 AM EDT
Today air travel is a minefield of delays, hassles and customer disappointment. Airlines struggle to revitalize the experience. GE and M2Mi will demonstrate practical examples of how IoT solutions are helping airlines bring back personalization, reduce trip time and improve reliability. In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect with GE, and Dr. Sarah Cooper, M2Mi's VP Business Development and Engineering, will explore the IoT cloud-based platform technologies driving this change including privacy controls, data transparency and integration of real time context w...
Oct. 9, 2015 07:30 AM EDT
"Matrix is an ambitious open standard and implementation that's set up to break down the fragmentation problems that exist in IP messaging and VoIP communication," explained John Woolf, Technical Evangelist at Matrix, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Oct. 9, 2015 07:00 AM EDT Reads: 5,880
WebRTC converts the entire network into a ubiquitous communications cloud thereby connecting anytime, anywhere through any point. In his session at WebRTC Summit,, Mark Castleman, EIR at Bell Labs and Head of Future X Labs, will discuss how the transformational nature of communications is achieved through the democratizing force of WebRTC. WebRTC is doing for voice what HTML did for web content.
Oct. 9, 2015 06:00 AM EDT Reads: 1,411
The IoT is upon us, but today’s databases, built on 30-year-old math, require multiple platforms to create a single solution. Data demands of the IoT require Big Data systems that can handle ingest, transactions and analytics concurrently adapting to varied situations as they occur, with speed at scale. In his session at @ThingsExpo, Chad Jones, chief strategy officer at Deep Information Sciences, will look differently at IoT data so enterprises can fully leverage their IoT potential. He’ll share tips on how to speed up business initiatives, harness Big Data and remain one step ahead by apply...
Oct. 9, 2015 05:15 AM EDT Reads: 511
Nowadays, a large number of sensors and devices are connected to the network. Leading-edge IoT technologies integrate various types of sensor data to create a new value for several business decision scenarios. The transparent cloud is a model of a new IoT emergence service platform. Many service providers store and access various types of sensor data in order to create and find out new business values by integrating such data.
Oct. 9, 2015 04:00 AM EDT Reads: 570
The broad selection of hardware, the rapid evolution of operating systems and the time-to-market for mobile apps has been so rapid that new challenges for developers and engineers arise every day. Security, testing, hosting, and other metrics have to be considered through the process. In his session at Big Data Expo, Walter Maguire, Chief Field Technologist, HP Big Data Group, at Hewlett-Packard, will discuss the challenges faced by developers and a composite Big Data applications builder, focusing on how to help solve the problems that developers are continuously battling.
Oct. 9, 2015 04:00 AM EDT Reads: 500
There are so many tools and techniques for data analytics that even for a data scientist the choices, possible systems, and even the types of data can be daunting. In his session at @ThingsExpo, Chris Harrold, Global CTO for Big Data Solutions for EMC Corporation, will show how to perform a simple, but meaningful analysis of social sentiment data using freely available tools that take only minutes to download and install. Participants will get the download information, scripts, and complete end-to-end walkthrough of the analysis from start to finish. Participants will also be given the pract...
Oct. 9, 2015 03:00 AM EDT Reads: 293
WebRTC services have already permeated corporate communications in the form of videoconferencing solutions. However, WebRTC has the potential of going beyond and catalyzing a new class of services providing more than calls with capabilities such as mass-scale real-time media broadcasting, enriched and augmented video, person-to-machine and machine-to-machine communications. In his session at @ThingsExpo, Luis Lopez, CEO of Kurento, will introduce the technologies required for implementing these ideas and some early experiments performed in the Kurento open source software community in areas ...
Oct. 9, 2015 03:00 AM EDT Reads: 728
Internet of Things (IoT) will be a hybrid ecosystem of diverse devices and sensors collaborating with operational and enterprise systems to create the next big application. In their session at @ThingsExpo, Bramh Gupta, founder and CEO of robomq.io, and Fred Yatzeck, principal architect leading product development at robomq.io, discussed how choosing the right middleware and integration strategy from the get-go will enable IoT solution developers to adapt and grow with the industry, while at the same time reduce Time to Market (TTM) by using plug and play capabilities offered by a robust IoT ...
Oct. 9, 2015 02:00 AM EDT Reads: 2,220
Today’s connected world is moving from devices towards things, what this means is that by using increasingly low cost sensors embedded in devices we can create many new use cases. These span across use cases in cities, vehicles, home, offices, factories, retail environments, worksites, health, logistics, and health. These use cases rely on ubiquitous connectivity and generate massive amounts of data at scale. These technologies enable new business opportunities, ways to optimize and automate, along with new ways to engage with users.
Oct. 9, 2015 02:00 AM EDT Reads: 167
The Internet of Things (IoT) is growing rapidly by extending current technologies, products and networks. By 2020, Cisco estimates there will be 50 billion connected devices. Gartner has forecast revenues of over $300 billion, just to IoT suppliers. Now is the time to figure out how you’ll make money – not just create innovative products. With hundreds of new products and companies jumping into the IoT fray every month, there’s no shortage of innovation. Despite this, McKinsey/VisionMobile data shows "less than 10 percent of IoT developers are making enough to support a reasonably sized team....
Oct. 9, 2015 02:00 AM EDT Reads: 209
“In the past year we've seen a lot of stabilization of WebRTC. You can now use it in production with a far greater degree of certainty. A lot of the real developments in the past year have been in things like the data channel, which will enable a whole new type of application," explained Peter Dunkley, Technical Director at Acision, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Oct. 9, 2015 01:45 AM EDT Reads: 7,028
Through WebRTC, audio and video communications are being embedded more easily than ever into applications, helping carriers, enterprises and independent software vendors deliver greater functionality to their end users. With today’s business world increasingly focused on outcomes, users’ growing calls for ease of use, and businesses craving smarter, tighter integration, what’s the next step in delivering a richer, more immersive experience? That richer, more fully integrated experience comes about through a Communications Platform as a Service which allows for messaging, screen sharing, video...
Oct. 9, 2015 12:00 AM EDT Reads: 1,135
SYS-CON Events announced today that Dyn, the worldwide leader in Internet Performance, will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Dyn is a cloud-based Internet Performance company. Dyn helps companies monitor, control, and optimize online infrastructure for an exceptional end-user experience. Through a world-class network and unrivaled, objective intelligence into Internet conditions, Dyn ensures traffic gets delivered faster, safer, and more reliably than ever.
Oct. 8, 2015 10:00 PM EDT Reads: 597
The IoT market is on track to hit $7.1 trillion in 2020. The reality is that only a handful of companies are ready for this massive demand. There are a lot of barriers, paint points, traps, and hidden roadblocks. How can we deal with these issues and challenges? The paradigm has changed. Old-style ad-hoc trial-and-error ways will certainly lead you to the dead end. What is mandatory is an overarching and adaptive approach to effectively handle the rapid changes and exponential growth.
Oct. 8, 2015 09:00 PM EDT Reads: 119
Mobile messaging has been a popular communication channel for more than 20 years. Finnish engineer Matti Makkonen invented the idea for SMS (Short Message Service) in 1984, making his vision a reality on December 3, 1992 by sending the first message ("Happy Christmas") from a PC to a cell phone. Since then, the technology has evolved immensely, from both a technology standpoint, and in our everyday uses for it. Originally used for person-to-person (P2P) communication, i.e., Sally sends a text message to Betty – mobile messaging now offers tremendous value to businesses for customer and empl...
Oct. 8, 2015 05:30 PM EDT Reads: 233
Can call centers hang up the phones for good? Intuitive Solutions did. WebRTC enabled this contact center provider to eliminate antiquated telephony and desktop phone infrastructure with a pure web-based solution, allowing them to expand beyond brick-and-mortar confines to a home-based agent model. It also ensured scalability and better service for customers, including MUY! Companies, one of the country's largest franchise restaurant companies with 232 Pizza Hut locations. This is one example of WebRTC adoption today, but the potential is limitless when powered by IoT.
Oct. 8, 2015 04:30 PM EDT Reads: 7,474
You have your devices and your data, but what about the rest of your Internet of Things story? Two popular classes of technologies that nicely handle the Big Data analytics for Internet of Things are Apache Hadoop and NoSQL. Hadoop is designed for parallelizing analytical work across many servers and is ideal for the massive data volumes you create with IoT devices. NoSQL databases such as Apache HBase are ideal for storing and retrieving IoT data as “time series data.”
Oct. 8, 2015 02:45 PM EDT Reads: 499