Linux and Open-Source Applications

The building blocks for a secure and trustworthy computer platform.

Can you trust your computer? This question is becoming increasingly important as both consumers and businesses adopt the Internet as a medium for financial transactions. Even more worrying is the number of computers with Internet access that are also used to store sensitive technical or corporate information. We feel that by using 128-bit encryption and similar techniques, many users are simply deluding themselves into thinking their data is secure.

The proliferation of Internet connections in the last few years is the source of a major security concern. The real threat is not to data traveling over secure connections, but rather comes from an inability to safeguard the data on the machine itself. By using open-source software as well as multiple software distribution channels, we believe potential network-related security problems can be largely eliminated.

Introduction

Credit-card information is often transmitted between users and commerce servers using 128-bit encryption provided through the “secure socket layer” in many web browsers. Information within financial organizations is usually transmitted through private links, relying on the integrity of the communications carrier to help ensure privacy, or through virtual private network links where network encryption devices protect the data.

While these methods of ensuring the secrecy of transmitted data have proven to be quite practical, they overlook what we consider to be a potentially far more serious security leak: direct Internet connection of computers at either end of the secure link, combined with the presence of untrustworthy application or operating-system software on those machines.

Worms, Viruses and Easter Eggs

The world's first major publicized experience of the damaging potential of a worm—a virus-like program that propagates through a network by taking advantage of security loopholes—was on November 2, 1988 (see Resources 1). A graduate student whose worm accidentally went wild managed to bog down thousands of Sun 3 and VAX computers that made up the backbone of the early Internet.

What is not so well-known is that the worm included a high-speed password-cracking algorithm, designed to allow it to gain access to more privileged operating-system functions. Had the worm been designed for espionage and operated at a much lower CPU priority level, it could well have scanned thousands of machines for “interesting” information and quietly sent data back to its author without anyone even noticing.

Computer users today are all too aware of the risks that viruses pose. Virus checkers are now commonly used to search out and destroy viruses that could do harm to a computer system. However, viruses are usually detected because of some action which they initiate to call attention to themselves. A virus developed for espionage would likely be explicitly designed to avoid doing anything that might call attention to its existence. As with the Internet worm, when armed with the appropriate technology to scan a system for interesting information, a virus could take advantage of an Internet-connected computer to “call home” with its findings and await further instructions.

What if the snooping software was intentionally loaded by the user and thus could never be detected by a virus checker? Easter eggs are sections of code within most common application software packages that can be activated by a series of undocumented commands. Eggs generally do something completely unrelated to the host application and unintended by the manufacturer. That isn't to say that eggs occur accidentally—they owe their existence to programmers who secretly add sections of code without any authorization from their employer to do so.

Most known Easter eggs are small and harmless, but as applications and operating systems have gotten larger over the last few years, it has become possible for rogue employees to include much more elaborate eggs and have them released with the finished product. An Easter egg that provides a good example of a significant amount of code being included in a popular product is the flight simulator in Microsoft Excel 97 (see Resources 2).

Word 97 has a surprising dictionary entry: if a sentence includes the word “zzzz”, the auto-spell-checker underlines it and offers “sex” as the corrected spelling. It's clear that Microsoft did not know about that entry when they released Word 97, and demonstrates the inability of the manufacturer to adequately monitor its programmers.

Virtually all versions of Microsoft Windows and application programs from other vendors also contain a plethora of Easter eggs (see Resources 3).

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