Why does Windows XP think that nobody else has ever heard of Ctrl-Alt-Del?
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At my age my memory is getting a little hazy, but that sequence is baked into the keyboard controller chip, irregardless of the OS.
Psychosis at 10 Film at 11 Those who do not remember the past, are doomed to repeat it. Those who do not remember the past, cannot build upon it.
At one time that was true, but I don't think it really applies any longer (USB keyboards).
Software Zen:
delete this; -
At one time that was true, but I don't think it really applies any longer (USB keyboards).
Software Zen:
delete this;You mean those new fangled doohickeys? Don't have any. All my computers run off my trusty programmable Gateway 2000 "Anykey" keyboards. Although for one machine I did have to get a PS2 to USB adapter. Silly thing kept losing characters.
Psychosis at 10 Film at 11 Those who do not remember the past, are doomed to repeat it. Those who do not remember the past, cannot build upon it.
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You mean those new fangled doohickeys? Don't have any. All my computers run off my trusty programmable Gateway 2000 "Anykey" keyboards. Although for one machine I did have to get a PS2 to USB adapter. Silly thing kept losing characters.
Psychosis at 10 Film at 11 Those who do not remember the past, are doomed to repeat it. Those who do not remember the past, cannot build upon it.
I'm not sure even PS/2 keyboard logic included the reset handling. IIRC, the original IBM PC keyboard did a processor reset when you hit Ctrl+Alt+Del. Obviously, with a USB device, that's no longer the case.
Software Zen:
delete this; -
Unless the system is running a different OS... nah, who would want that? :confused:
Why would you be reading a Windows message if you are running a different OS? The point is that if someone tries to steal your password by displaying a fake login screen, the Ctrl+Alt+Del combo will defeat that trick. It is reasonable to hate on Windows for a whole host of things, but this is not one of them.
Narf.
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I've always wondered this about Windows XP - before you log in, you have to press Ctrl-Alt-Del to "unlock the computer", and if you go to the help screen on the unlock dialog, it will tell you that it's for "security" because "only Windows recognizes Ctrl-Alt-Del". Now, what in the hell was Microsoft smoking? Windows is not the only program that can recognize Ctrl-Alt-Del! Anyone have any idea what is going on here?
Because the hardware of the keyboard controller sends send a hardware interrupt to the CPU when that magic combo is pressed. It was purposely selected (by IBM, before Microsoft even existed) to require using both hands because it used to be (back in the days of DOS) the interrupt that reset your computer, causing it to immediately reboot and you to loose whatever work you were in the middle of. A hardware interrupt to the CPU causes it to drop whatever it is doing and starts running code from the installed interrupt handler at the next instruction. This makes it just that much harder for malware to trap and spoof, and significantly harder for it to do so without the OS being able to notice. I'm not sure ctl-alt-del still generates a hardware level interrupt anymore.. doesn't really matter anyway nowdays. If you were around back then, it was kind of an odd transition to get used to walking up to a computer and press the reboot-immediately magic key combo in order to, not reboot it, but merely log in. That level of security was also pretty radical at the time -- most (multiuser) systems didn't bother with such stuff, you indicated you wanted to log in by starting to type at the keyboard.
We can program with only 1's, but if all you've got are zeros, you've got nothing.
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It means only windows, rather than a driver or program.
That's not true. If a programmer know what he's doing he can easily write a program to load a custom GINA driver that can trap the Ctrl+Alt+Del sequence instead of it beeing trapped by the winlogon process. It's not that difficult to bypass this security mechanism.
"To alcohol! The cause of, and solution to, all of life's problems" - Homer Simpson
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I've always wondered this about Windows XP - before you log in, you have to press Ctrl-Alt-Del to "unlock the computer", and if you go to the help screen on the unlock dialog, it will tell you that it's for "security" because "only Windows recognizes Ctrl-Alt-Del". Now, what in the hell was Microsoft smoking? Windows is not the only program that can recognize Ctrl-Alt-Del! Anyone have any idea what is going on here?
I agree with you. But very few programmers know that is possible and even fewer no how to load a custom GINA driver that can trap the Ctrl+Alt+Del sequence instead of it being trapped by winlogon. It's not very common to see it, but then The statement provided by the help screen is not true.
"To alcohol! The cause of, and solution to, all of life's problems" - Homer Simpson
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I've always wondered this about Windows XP - before you log in, you have to press Ctrl-Alt-Del to "unlock the computer", and if you go to the help screen on the unlock dialog, it will tell you that it's for "security" because "only Windows recognizes Ctrl-Alt-Del". Now, what in the hell was Microsoft smoking? Windows is not the only program that can recognize Ctrl-Alt-Del! Anyone have any idea what is going on here?
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No, you will still be able to log in with Remote Desktop, but a hacker trying to take control of your machine through any open ports won't be able to simulate the Ctrl-Alt-Del to gain access. Any keystrokes he sends won't be put into the login screen, since it's not active.
Karl - WK5M PP-ASEL-IA (N43CS) PGP Key: 0xDB02E193 PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193
Sure he (the hacker) can :D depends on the kind of access he gains. You can intercept and replicate remotely any key sequence you want (not to mention that all remote control software can do that, but if you ever played with trojans you would know :P). So no - that's not the reason.
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I've always wondered this about Windows XP - before you log in, you have to press Ctrl-Alt-Del to "unlock the computer", and if you go to the help screen on the unlock dialog, it will tell you that it's for "security" because "only Windows recognizes Ctrl-Alt-Del". Now, what in the hell was Microsoft smoking? Windows is not the only program that can recognize Ctrl-Alt-Del! Anyone have any idea what is going on here?
As I recall from a NT Workstation class in 1998 or '99, this was a requirement from the government that a human had to initiate the login process. C-A-D would not be accepted by the login process from within Windows, it had to come from the keyboard. Sort of an early two-factor login process. Maybe not the best explanation, but that's the best I can do after 13 years.
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That's not true. If a programmer know what he's doing he can easily write a program to load a custom GINA driver that can trap the Ctrl+Alt+Del sequence instead of it beeing trapped by the winlogon process. It's not that difficult to bypass this security mechanism.
"To alcohol! The cause of, and solution to, all of life's problems" - Homer Simpson
What's a GINA driver?
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What's a GINA driver?
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Thanks! I googled "GINA driver" and got nothing. So this is pre-Vista only. Somehow I think Microsoft would be aware that this is a security threat. I hadn't heard of this being used in a virus. But you probably have some experience with it.
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Thanks! I googled "GINA driver" and got nothing. So this is pre-Vista only. Somehow I think Microsoft would be aware that this is a security threat. I hadn't heard of this being used in a virus. But you probably have some experience with it.
Yes, it is pre-Vista. Although the model changed for Vista, it's still possible to accomplish the same. It's a very obscure topic with scarce documentation and that very few people know about. There's definitely virus or other malicious malwares around that exploit this. But since this requires elevated privileges, the user would need to explicit allow a program to make modifications on the logon service. The most common examples for changing the default behavior for the windows logon are the personalized logons created by laptop manufacturers. The same way they personalize the way the login is performed (some with face recognition, etc), they can also intercept the Ctrl+Alt+Del and even forward the keystrokes if they desire, so other applications can also catch the Ctrl+Alt+Del.
"To alcohol! The cause of, and solution to, all of life's problems" - Homer Simpson
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I've always wondered this about Windows XP - before you log in, you have to press Ctrl-Alt-Del to "unlock the computer", and if you go to the help screen on the unlock dialog, it will tell you that it's for "security" because "only Windows recognizes Ctrl-Alt-Del". Now, what in the hell was Microsoft smoking? Windows is not the only program that can recognize Ctrl-Alt-Del! Anyone have any idea what is going on here?
The CTRL-ALT-DEL requirement is only present in the "Professional" version of XP as well as every Microsoft server since Windows NT. The Home version shows user names on the initial page. It can be turned off using Administrative Tools - Local Security Policy. Follow the path: Security Settings, Local Policies, Security Options and look for an entry called "Interactive logon: Do not require CTRL+ALT+DEL". As far as "not the only program", what do you mean? One can execute a CTRL-ALT-DEL sequence while Windows is running to display the Security dialog or Task Manager, depending on which version of Windows you're using. As a result, no other "program" can use that sequence after Windows is running. The only other CTRL-ALT-DEL sequence is during boot, after BIOS is loaded but before Windows starts loading. It's sole purpose is to reboot the computer if it gets hung. I don't recall any other instances for that particular sequence. There is a video on YouTube of IBM's Dave Bradley explaining why and how he invented the sequence and should prove hilarious to the older among us that get the joke. Link: http://www.youtube.com/watch?v=1zADyh0JQh8