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This chapter is from the book

1.4 Threats to Software Security

In information security, the threat—the source of danger—is often a person intending to do harm, using one or more malicious software agents. Software is subject to two general categories of threats:

  • Threats during development (mainly insider threats). A software engineer can sabotage the software at any point in its development life cycle through intentional exclusions from, inclusions in, or modifications of the requirements specification, the threat models, the design documents, the source code, the assembly and integration framework, the test cases and test results, or the installation and configuration instructions and tools. The secure development practices described in this book are, in part, designed to help reduce the exposure of software to insider threats during its development process. For more information on this aspect, see "Insider Threats in the SDLC" [Cappelli 2006].
  • Threats during operation (both insider and external threats). Any software system that runs on a network-connected platform is likely to have its vulnerabilities exposed to attackers during its operation. Attacks may take advantage of publicly known but unpatched vulnerabilities, leading to memory corruption, execution of arbitrary exploit scripts, remote code execution, and buffer overflows. Software flaws can be exploited to install spyware, adware, and other malware on users' systems that can lie dormant until it is triggered to execute.4

Weaknesses that are most likely to be targeted are those found in the software components' external interfaces, because those interfaces provide the attacker with a direct communication path to the software's vulnerabilities. A number of well-known attacks target software that incorporates interfaces, protocols, design features, or development faults that are well understood and widely publicized as harboring inherent weaknesses. That software includes Web applications (including browser and server components), Web services, database management systems, and operating systems. Misuse (or abuse) cases can help project managers and software engineers see their software from the perspective of an attacker by anticipating and defining unexpected or abnormal behavior through which a software feature could be unintentionally misused or intentionally abused [Hope 2004]. (See Section 3.2.)

Today, most project and IT managers responsible for system operation respond to the increasing number of Internet-based attacks by relying on operational controls at the operating system, network, and database or Web server levels while failing to directly address the insecurity of the application-level software that is being compromised. This approach has two critical shortcomings:

  1. The security of the application depends completely on the robustness of operational protections that surround it.
  2. Many of the software-based protection mechanisms (controls) can easily be misconfigured or misapplied. Also, they are as likely to contain exploitable vulnerabilities as the application software they are (supposedly) protecting.

The wide publicity about the literally thousands of successful attacks on software accessible from the Internet has merely made the attacker's job easier. Attackers can study numerous reports of security vulnerabilities in a wide range of commercial and open-source software programs and access publicly available exploit scripts. More experienced attackers often develop (and share) sophisticated, targeted attacks that exploit specific vulnerabilities. In addition, the nature of the risks is changing more rapidly than the software can be adapted to counteract those risks, regardless of the software development process and practices used. To be 100 percent effective, defenders must anticipate all possible vulnerabilities, while attackers need find only one to carry out their attack.

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