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Open Source Advantages

You and your company can use open source both to cut costs and improve your security. The following sections touch on the myriad of reasons why open source security tools might make sense for you and your company.


It's hard to beat free! Although open source does not necessarily always mean free, most open source software is available at no charge. The most common open source license is the GNU GPL license, which is a free software license. Other open source software might be shareware or even charge up front, like the commercial servers available from RedHat. But either way, open source is usually available for a fraction of the cost of commercial alternatives. This helps greatly in justifying new security projects within your company. When all that is needed is a little of your time and maybe a machine to run the software, it is a lot easier to get approval for a new solution. In fact, depending on your authority level, you may be able to go ahead and implement it without having to make a business case for it. If you want to take it a step further, after successful installation, you can bring the results to your boss and demonstrate that you saved the company thousands of dollars while making the network more secure (and that may improve your job security!).


By definition, open source software is modifiable and extendable, assuming you have the programming skills. Many open source programs have scripting languages built in so that you can write small add-on modules for them without having to be a programming guru. Nessus, the open source vulnerability scanner does this with their NASL scripting language (this is demonstrated later in this book, and you'll learn how to write some custom security tests too). Snort, the open source intrusion detection system mentioned earlier, lets you write your own alert definitions. This means that if there is something specific to your company that you need to test for, you can easily write a custom script to look for it. For example, if you have a database file called customer.mdb that is specific to your company and that should only be used by certain departments, you could write a Snort rule that looks for that file traversing the network and alerts you.

And of course if you are a real programming guru, you can get involved in contributing to the core code and gain both valuable experience and recognition within the open source community. This could also be helpful in terms of your job marketability.


There are some people, mostly those involved with commercial software concerns, who advocate that closed source software is inherently more secure since hackers do not have the internal workings of the software easily available to them. This school of thought relies on the security premise of obfuscation—keeping the design of your product secret. However, this logic breaks down when you look at the facts. Windows is the largest proprietary software product in the world, yet the number of security holes announced in the Windows platforms is about the same as those found in Linux and other open source platforms. The truth is that whether the source code is open or closed doesn't make programmers write more secure programs.


Discovery and remediation of security issues in software can be much faster with open source programs. Commercial companies often have strong monetary motivations for not admitting to security flaws in their products. Multiple security holes found in a product, especially if it is a security product, could hurt sales to new customers. If it is a publicly traded company, the stock price could fall. Additionally, developing security patches and distributing them to customers are expensive endeavors, ones that usually don't generate any revenue. So getting a company to confirm a security issue with its software can be a major effort. This means days or weeks can go by while customer systems are still vulnerable. Frustration with this process has prompted some security researchers to adopt a policy of releasing new security vulnerabilities directly to the public rather than privately to the company.

Once a security hole is known to the public, a company will often go through a complicated development and testing process before releasing a patch to the public, ensuring that there aren't any liability issues and that the patch can be released for all platforms at once. So more time may go by while you have a known security hole that hackers can exploit.

Open source software projects have no such limitations. Security patches are usually available within hours or days, not weeks. And of course you don't have to wait for an official patch; if you understand the code well enough, you can write your own or design a workaround while you wait for one.

The general thinking in the open source community is that the best overall security comes from a critical review by a large body of people who don't have a vested interest in not finding any holes. This is the same measure of quality that cryptographic researchers apply to their work. The open source concept, while not guarantying that you will get more secure software, means you don't have to take a company's word that a product is secure, and then wait for them to come up with a solution for any security holes.

User Support

Commercial software products usually have support lines and a formal channel to go through for help. One of the main reasons many people shy away from open source solutions is that they feel like they have to pay for a product to get decent support. However, the support you often get for your money is not that great. If the software company is small, you might have to wait hours or days for a return call. If the vendor is large, you will probably be shunted into a call queue. When you finally get connected, it will be with an entry-level technical person who can't do much more than enter your problem into a knowledge base to see if anyone has had the problem before and then parrot back a generic solution. Usually you have to get to a level two or three technician before you get someone who truly understands the product and can help you with complicated problems. Not to mention that companies don't like to admit their products have bugs; they will tend to blame it on everything else beside their product (your operating system, your hardware, and so on).

Add to that, many companies are now charging separately for support. The price you pay over several years for support of the software can exceed the initial purchase price of it. These charges create a nice steady stream of revenue for the company even if you never upgrade. Most software companies, if they aren't already doing it, are moving in this direction. Toll-free numbers for software technical support are becoming a thing of the past.

Open source products often have terrific support networks, albeit somewhat nontraditional. Open source support is less organized but often more helpful and more robust. There will rarely be a phone number to call, but there are usually several options to get answers on the software. On a smaller project, it might be as simple as e-mailing the developer directly. The larger packages usually have a mailing list you can post questions to. Many have several different lists depending on your question (user, developer, specific modules, or platforms). Many now have chat rooms or IRC channels where you can ask questions, ask for new features, or just sound off in real time.

The neat thing is that you are usually talking to people who are very familiar with the software, possibly even the actual developers. You can even ask them for new features or comment on recently added ones. You will end up talking to some of the brightest and most experienced people in the industry. I've learned a lot by just following the conversations on the mailing lists.

Most questions I've posed to these lists have been answered in a few hours or less. The answers are usually insightful and informative (and sometimes witty). You will often get several different opinions or solutions to your problem, all of which may be right! Besides getting very detailed answers to your questions, you can talk about the state of the art in that particular area or engage in philosophical debates about future versions, and so forth (if you have a lot of extra time on your hands). And of course, if you are knowledgeable about the software, you are free to chime in with your own answers to questions.

Keep in mind that these folks usually aren't employees of a company producing the software and might sometimes seem a bit harsh or rude. Asking simple questions that are answered fully in the INSTALL pages or in a FAQ might earn you a rebuke. But it will also usually get you the answer or at least a pointer to where you can find it. Sometimes the flame wars on the lists crowd out the real information. However, I'll take impassioned debate over mindless responses any day.

Finally, if you really do feel like you have to pay for support, there are companies that do just that for open source platforms. Numerous Linux companies offer supported versions of that open source operating system. Many of the more popular applications also have companies providing support for them. You can buy a prepackaged Snort IDS box from several companies that will support you and provide regular updates. This way you can have the same vaulted support that commercial products offer but still keep all the benefits of an open source platform.

Product Life Span

With commercial software, you are at the mercy of the corporation that owns the product you select. If it's a large company like Microsoft, then you are probably in good shape. However, even Microsoft has tried to get into market segments and then decided they wanted out and dropped product lines. Smaller companies could go out of business or get bought or merged. In this day and age, it is happening more and more. If the company that buys them has competing products, more than likely they will get rid of one of the lines. If they decide to drop your product, then you are out of luck for future support. With a closed source product, you have no way of asking any questions or making any necessary upgrades to it once the company decides they don't want to play anymore.

Open source projects never die a final death. That's not to say that they don't go dormant. Projects go by the wayside all the time as the participants graduate or move on to a new stage of life. This is more prevalent in the smaller programs and tools. The larger ones (which comprise the majority of programs mentioned in this book) always have someone willing to step up and grab the reins. In fact, there are sometimes power struggles in the hierarchy for control of a project. However, if someone doesn't like the direction it is going, there is nothing to stop him or her from branching off and taking the product where he or she wants it to go. Even in the smaller ones, where there is a single developer who might not be actively developing it anymore, you can simply pick up where they left off. And if you need to fix something or add a feature, the code is wide open to let you do that. With open source software, you are never at the mercy of the whims of the market or a company's financial goals.



If you want to learn about how security software works or polish your programming skills, open source software is a great way to do it. The cost is low, so you don't have to worry about dropping a couple of thousand dollars on training or programs. If you are doing this yourself, all you need is a machine to run it on and an Internet connection to download the software (or the CD-ROM included with this book). If you are doing it for a company, it is the cheapest training course your company will ever approve. Plus, your company has the added benefit that you will be able to use the technology to improve the company's computer security without spending a lot of money. Talk about a win-win situation!

Of course, budding programmers love open source software because they can get right into the guts of the program and see how it works. The best way to learn something is to do it, and open source software offers you the ability to see all the code, which is usually fairly well documented. You can change things, add new features, and extend the base code—all things that are impossible with closed source software. The most you can ever be with a closed source program is an experienced user; with open source, you can be an innovator and creator if you want.

The mailing lists and chat rooms for open source projects are excellent places to ask questions and make friends with people who can really mentor your career. Getting involved with an open source project is probably the quickest way to learn about how software is developed. Which leads into my next point.


After you've cut your teeth, gotten flamed a few times, and become a regular contributing member of an open source package, you will notice that you are now the go-to guy for all the newbies. Building a reputation in the open source world looks great on a resume. Being able to say you were integrally involved in the development of an open source product speaks volumes about your dedication and organization skills, not to mention your programming skills. Designing an open source software package makes for a great graduate research project. And of course, once you get good enough, you may end up producing your own open source software and building quite a following. More than a few authors of open source software have gone on to parley their user base into a real company making real money. So whether your efforts in open source are just a hobby, as most are, or become your sole aim in life, it can be very rewarding and a lot of fun.

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