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I was trying to close a non-responsive process, and after the first time I clicked "End Process", nothing happened. So I did it again and this time a window popped up saying "Access is Denied". Eventually the process did close, but this got me thinking..

If I had ran task manager as an administrator, would it have still gave me this "Access is Denied" message? Or, in-fact, does Windows 10 run task manager as an administrator by default (when the user account is an administrator). Furthermore, is there any difference between running it as administrator or not?

Running it as admin via this method:

I don't see any noticeable differences between that and just doing Ctrl+Shift+Escape.

Note: This question is specifically for Windows 10 (and possibly 8/8.1) and I am running Pro. Also, my UAC set to 'Never notify'.

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If UAC is off and you use Administrator account, then each process you start runs with Administrator privileges. – Alexey Ivanov Jan 20 at 9:32
    
@AlexeyIvanov I don't believe that's true. Maybe some, but not all processes and applications.. – Insane Jan 20 at 9:38
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You're right: that's changed with Windows 8: The behavior of UAC for the "Never notify" setting no longer disables UAC. The "Never notify" setting gives you a split token and always automatically elevates the privilege required. … You can still disable UAC by using Group Policies or manually setting the registry key. Source: User Account Control. But if you disable UAC completely, then all processes are started with Administrator privileges. – Alexey Ivanov Jan 20 at 10:06
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@AlexeyIvanov And now that I've disabled UAC from Group Policy, you're right! Everything is running elevated now. – Insane Jan 20 at 10:21
    
Yep. Though IIRC Windows Metro apps are dependant on not elevating. – qwertyuiop Jan 20 at 13:25
up vote 33 down vote accepted

Does task manager run as administrator by default on Windows 10?

Only if it is being run from an administrator account. Ben N's answer below has a great explanation of how this is actually implemented.

If I had ran task manager as an administrator, would it have still gave me this "Access is Denied" message?

Yes. There are plenty of processes that even an administrator is not permitted to end. Furthermore, trying to end a non-existent task also produces this error message.

If the reason you had got the "Access is Denied" message was due to Task Manager not running as Administrator, you would get this very explicit message telling you so:

enter image description here

Furthermore, is there any difference between running it as administrator or not?

Yes, but you'd have to run it from a non-administrator account to see it.

Incidentally all the above behaviours are exactly the same as in Windows 8/8.1

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+1, because this is very well explained. :) – LPChip Jan 19 at 23:21
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Indeed it is. Covers all points, but I'm inclined to give 48 hours for other answers to have a chance (as I've got yelled at on multiple occasions for accepting too soon :) – Insane Jan 19 at 23:38
    
In my experience, this is usually happens when a process is stuck waiting for a kernel-mode I/O request to complete. See “Access denied” when trying to end a process on Windows 8 – Christopher Oicles Jan 20 at 3:01
    
It is possible to end those processes if you start taskmgr as SYSTEM though, by using "psexec -d -i -s taskmgr" – drake7707 Jan 20 at 13:22
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@drake7707 Actually, protected processes cannot be terminated or even write-DAC'd from user mode, even if you're running as SYSTEM. I don't believe user mode can authoritatively deal with processes that are hung in kernel mode either; you have to close all the handles (see another of my answers) and wait for all kernel-mode requests to complete. – Ben N Jan 20 at 14:15

The existing answer is very good. I'll provide some technical details, for those that like such things.

Taskmgr.exe (in \Windows\System32) is the program that is run when you call for Task Manager. Inspecting it with a hex editor, I discovered that its manifest sets requestedExecutionLevel to highestAvailable. This means that if you are running as a local admin, Task Manager will require you to elevate. You can easily demonstrate this by setting UAC to the highest level and pressing Ctrl+Shift+Esc to launch Task Manager, noting that it produces an elevation prompt. If UAC is not at the highest level, Task Manager can silently elevate because it's an integral Windows component. In short, yes, Task Manager runs as admin by default when possible.

highestAvailable (as opposed to requireAdministrator) allows non-admins to run the program without being asked to elevate, but they of course won't be able to do anything administrative from it.

A quick-and-dirty way to see if a program is running elevated is to enable the UAC virtualization column in the Details tab of Task Manager. If and only if a process's entry in that column is Not allowed, then it is elevated. (Administrative processes cannot be compatibility-redirected.) You could also check whether it has the powerful privileges (e.g. SeSecurityPrivilege) using Sysinternals Process Explorer.

In response to your question about still being denied access to some processes, Windows has a concept of protected processes that absolutely cannot be touched from user mode, not even by processes running as SYSTEM; the protection is enforced by the kernel. Only essential system services get this kind of guarding. One such process is csrss.

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A lot of antivirus applications (including Microsoft's own) are also protected. – qwertyuiop Jan 20 at 12:23

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