Myth: There's Safety In Small Numbers

Perhaps the most oft-repeated myth regarding Windows vs. Linux security is the claim that Windows has more incidents of viruses, worms, Trojans and other problems because malicious hackers tend to confine their activities to breaking into the software with the largest installed base. This reasoning is applied to defend Windows and Windows applications. Windows dominates the desktop; therefore Windows and Windows applications are the focus of the most attacks, which is why you don't see viruses, worms and Trojans for Linux. While this may be true, at least in part, the intentional implication is not necessarily true: That Linux and Linux applications are no more secure than Windows and Windows applications, but Linux is simply too trifling a target to bother attacking.

This reasoning backfires when one considers that Apache is by far the most popular web server software on the Internet. According to the September 2004 Netcraft web site survey, [1] 68% of web sites run the Apache web server. Only 21% of web sites run Microsoft IIS. If security problems boil down to the simple fact that malicious hackers target the largest installed base, it follows that we should see more worms, viruses, and other malware targeting Apache and the underlying operating systems for Apache than for Windows and IIS. Furthermore, we should see more successful attacks against Apache than against IIS, since the implication of the myth is that the problem is one of numbers, not vulnerabilities.

Yet this is precisely the opposite of what we find, historically. IIS has long been the primary target for worms and other attacks, and these attacks have been largely successful. The Code Red worm that exploited a buffer overrun in an IIS service to gain control of the web servers infected some 300,000 servers, and the number of infections only stopped because the worm was deliberately written to stop spreading. Code Red.A had an even faster rate of infection, although it too self-terminated after three weeks. Another worm, IISWorm, had a limited impact only because the worm was badly written, not because IIS successfully protected itself.

Yes, worms for Apache have been known to exist, such as the Slapper worm. (Slapper actually exploited a known vulnerability in OpenSSL, not Apache). But Apache worms rarely make headlines because they have such a limited range of effect, and are easily eradicated. Target sites were already plugging the known OpenSSL hole. It was also trivially easy to clean and restore infected site with a few commands, and without as much as a reboot, thanks to the modular nature of Linux and UNIX.

Perhaps this is why, according to Netcraft, 47 of the top 50 web sites with the longest running uptime (times between reboots) run Apache. [2] None of the top 50 web sites runs Windows or Microsoft IIS. So if it is true that malicious hackers attack the most numerous software platforms, that raises the question as to why hackers are so successful at breaking into the most popular desktop software and operating system, infect 300,000 IIS servers, but are unable to do similar damage to the most popular web server and its operating systems?

Viruses, Trojans and other malware make it onto Windows desktops for a number of reasons familiar to Windows and foreign to Linux:

1. Windows has only recently evolved from a single-user design to a multi-user model
2. Windows is monolithic, not modular, by design
3. Windows depends too heavily on an RPC model
4. Windows focuses on its familiar graphical desktop interface