Administering Windows Vista Security: The Big Surprises by Byron & Minasi Hynes & Byron & Minasi Hynes

Author:Byron & Minasi Hynes & Byron & Minasi Hynes [Hynes, Byron & Minasi, Mark]
Language: eng
Format: epub
Tags: Computers, General, Networking, Windows Workstation, Operating Systems, Microsoft Windows (Computer File), Computer Security, Security
ISBN: 9780470108321
Publisher: Wiley/Sybex

Running in kernel mode. In the Windows world, programs either run as "user mode" or "kernel mode." Almost every program that you've ever installed on Windows runs in user mode: word processors, Web browsers, e-mail clients, games, spreadsheets, databases, and so on all run in user mode. The beauty of user mode is that each user mode application is placed in its own little "memory compartment" that it cannot write outside of. It is, then, impossible for a bug in a copy of Notepad to cause Notepad to overwrite some of the memory space allocated to, say, Calculator; when Notepad tries, it will trigger an error that will cause Windows to close down Notepad and ask you if Vista can send a trouble report to Microsoft about it. Kernel mode code, in contrast, can mess with whatever part of memory that it wants to, so buggy kernel mode programs can do a lot of damage. Basic operating system components, device drivers, and a lot of malware are three examples of commonly encountered kernel mode programs. (That's why one of the easiest ways to make your system unstable is to install a buggy driver. Or, I suppose, some malware!) The bottom line is that about the only kernel mode code you're ever going to be aware of installing is a device driver, and I can't see why a device driver would want to write to any of the protected locations. Virtualization would be fairly unnecessary for device drivers anyway, as they typically run with the token of the LocalSystem account, which has permissions to do just about anything anyway—it may be powerful, but it doesn't fall under Administrator Approval Mode. (If it did, you'd have to respond to about a thousand Consent UIs just to get a computer booted up!)

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