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Eddie
Asked: 2009-05-02 16:51:23 +0800 CST

How does CTRL-ALT-DEL to log in make Windows more secure?

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When logging into Windows, it says on that page that CTRL-ALT-DEL somehow makes Windows more secure. I have never been able to figure a mechanism where having to press some specific key combination before logging in makes the system more secure. I have never encountered a VMS, UNIX or related system that makes you press any key to log in -- except older terminal-based UNIXes where you press ENTER to get a login prompt.

How does having to press CTRL-ALT-DEL before logging in make Windows more secure?

windows security

7 Answers

  1. Best Answer

    The Windows (NT) kernel is designed to reserve the notification of this key combination to a single process: Winlogon. So, as long as the Windows installation itself is working as it should - no third party application can respond to this key combination (if it could, it could present a fake logon window and keylog your password ;)

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  2. CTRL+ALT+DEL the history

    Actually, I was just trying to solve a development problem that we had: brand new hardware, brand new software, you're testing this stuff out, it would hang up all the time. So the only solution you had was to turn the power off, wait a few seconds, turn the power back on, wait for it to go through the power on self test. I said, I'm writing all this code for the keyboard, I can .. let's just shortcut it. I originally intended for it to be what we would now call an easter egg, just something we were using in development, it wouldn't be available elsewhere. But then the pubs people found out about it. They're trying to figure out how to tell somebody to start up one of their programs, and they had the answer: just put the diskette in, hit CTRL+ALT+DEL, and by magic your program starts. So, it was like a five minute job in doing it. I didn't realize that I was going to create a cultural icon when I did it. But I have to share the credit; I may have invented it, but I think Bill [Gates] made it famous.

    http://www.youtube.com/watch?v=1zADyh0JQh8

    Quite a funny and informative clip, actually!

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  3. Ctrl-Alt-Del is a Secure Attention Key that helps to prevent login spoofing.

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  4. Only programs with the highest operating privileges can hook that interrupt. Since the operating system reserves that privilege level for itself and won't let user programs run at that level, user level programs can't respond to that keystroke.

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  5. It's explained in the 'Help' link on the window that tells you to type Ctrl-Alt-Del.

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  6. How does having to press CTRL-ALT-DEL before logging in make Windows more secure?

    No program running under Windows can hook Ctrl-Alt-Del,

    so iff the box is running Windows you can be assured there's no login spoofing. Of course, it's trivial (FSVO "trivial") to spoof a Windows login screen complete with Ooh-Magic-Keys handling, and thus capture username/password pairs, by running Not-Windows.

    Thus the answer to the OP's question is, fundamentally, In No Way.

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  7. Just something that kinda relates to this:

    You can copy the command prompt into the login screen using a LiveCD and start it using the enable sticky keys shortcut (e.g. Shift+Shift+Shift+Shift+Shift). Which is really bad/good depending on how you use it (e.g. You can reset passwords using net user command).

    Read more here: http://www.hackforums.net/printthread.php?tid=73864

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