Chapter 4: Hacking Windows

INTRODUCTION

By most accounts, systems running Microsoft's Windows family of operating systems comprise a significant portion of any given network, private or public. Largely because of this prevalence, Windows has remained a dedicated target of the hacking community since at least 1997, when a researcher named "Hobbit" released a paper on the Common Internet File System (CIFS) and Server Message Block (SMB), the underlying architectures of Windows networking. (You can find a copy of the paper at http://www. insecure .org/stf/cifs.txt.) The steady release of Windows exploits hasn't abated.

Microsoft has diligently patched most of the problems that have arisen and has slowly fortified the Windows lineage with new security- related features as it has matured. Most significantly, with the advent of Windows XP, Microsoft for the first time offered both businesses and consumers a platform based on the NT kernel, which was formerly focused primarily on the needs of the enterprise such as built-in networking support, scalability, fault tolerance, and security. Therefore, we think the common perception of Windows as an insecure platform is simply uninformed. In knowledgeable hands, Windows can be just as secure as any other system, be it based on UNIX, Linux, or any other OS. As an old security saying goes, "The driver bears more responsibility than the car."

Note 

This chapter will treat only Windows XP and Server 2003 and later versions, since most previous versions are no longer under mainstream support.

Clearly, however, this chapter would not be as lengthy as it is if Windows were 100percent secure out of the box. In thinking about and observing Windows security over many years , we've narrowed the areas of highest risk down to two factors: popularity and default insecure configuration.

Popularity is a two-sided coin for those running Microsoft technologies. On one hand, you reap the benefits of broad developer support, near-universal user acceptance, and a robust worldwide support ecosystem. On the flip side, the dominant Windows monoculture is increasingly becoming the target of choice for hackers who craft sophisticated exploits and then unleash them on a global scale (Internet worms based on Windows vulnerabilities such as Code Red, Nimda, Slammer, Blaster, Sasser, and so on all testify to the persistence of this problem). When it comes to notoriety among hackers (both legitimate and illegitimate), there is no bigger feather in the cap than to tar Microsoft.

At the risk of oversimplifying, default insecure configurations have historically made this monoculture so easy to mow down. There are several corollaries to this principle: ease of use, legacy support, and a burgeoning feature set.

The perceived simplicity of the Windows interface makes it appealing to novice administrators who typically adjust few Windows settings once they get the shrink-wrap off. This simplicity is deceptive, howeveras any experienced Windows administrator knows , there are dozens of settings that must be tweaked to ensure solid system security (hence the reason for this book!).

Legacy support confounds this problem and makes Windows less secure than it could be. As you will see in this chapter, Windows' continued reliance on legacy features left over from its LAN-based heritage leave it open to some simple attacks. Of course, this legacy support is enabled by default out-of-the-box configurations.

Finally, what keeps Windows squarely in the sights of hackers is the continued proliferation of features and functionality enabled by default within the platform. For example, it has taken three generations of the operating system for Microsoft to realize that installing and enabling Windows' Internet Information Services (IIS) extensions by default leaves its customers exposed to the full fury of public networks (both Code Red and Nimda targeted IIS, for example). One of the cardinal rules of security is that the security risk to any system is directly proportional to its complexity, and Microsoft seems to only now be beginning to learn from its past sins of enabling the maximum functionality out of the box.

There are some signs that the message is beginning to sink in. In January 2002, Microsoft's corporate and spiritual leader, Bill Gates, sent out a memo to the company elaborating on a concept called "Trustworthy Computing" (TwC). TwC seeks to set the same expectations for Microsoft products that consumers have come to associate with the more mundane technologies of daily life, such as dial tone, running water, and electricity. More important than these high concepts was the statement in the memo that security should come before new features in future development projects at Microsoft. It was subsequently reported that the release of Microsoft Windows Server 2003 was delayed while Microsoft performed a "security push" to examine the design and implementation of the product for possible weaknesses. This push seems to be paying dividends in terms of a reduced number of security vulnerabilities in Windows Server 2003 versus its predecessors.

As always, however, only time will tell how great the dividendrecall that it wasn't until Windows NT4 Service Pack 3 that some of the OS's current core security features (such as SYSKEY) were added, and until around Windows 2000 Service Pack 2 that some of the most critical IIS flaws were uncovered and addressed, all in response to devious attacks cobbled together by an ever- tenacious hacking community. At the time of this writing, we give Microsoft a C+ on Windows security, mostly because of the apparent improvements made to IIS, which hasn't seen a serious security bug since our last edition of this book. Of course, other significant flaws have been found elsewhere in the OS, and we will spend significant time with these in this chapter.

Note 

In particular, Internet Explorer, the web browser that comes with Windows, remains a major source of security pain. See Chapter 13 for more information about IE security attacks and countermeasures.

So, now that we've taken the 100,000- foot view of Windows security, let's review where we are and then delve into the nitty-gritty details.