From a programmer's perspective, I would suggest your try learning programming using windows API, and further more - API hooks.
The OS kernel keeps a table of these native API functions which you need to identify and hook into. Your hook will then redirect and modify/filter the output. This piece of code has to run on kernel-space, and in order for you to control it (i.e. load/stop), you'd have to have a piece of software on the user-space as well. Although these are possible on the user-space as well, it will most likely be flagged by modern AVs as some sort of malicious activity.
The approach would be to hook a piece of code to intercept API calls (i.e.NtQueryDirectoryFile()) such that you modify/filter the output - sort of man-in-the-middle approach. Processes running on user-space(i.e. TaskManager,Windows Explorer,Process Explorer), will just display the filtered output provided by your hook... And NO, ACLs has no power on this layer
Of course, modern AVs has pieces of code running on kernel-space too, and/or PATTERN MATCHING (remember when AV updates are called AV Patterns Update? ) - to detect and prevent such malicious hooks.
Does this apply to Windows 7 and 8.x ? – Faiz – 2015-04-20T04:33:53.167
@Faiz the "Use an antivirus" part does. You should always use an antivirus (there are free ones such as Avast Antivirus), and these days it is even necessary to use antivirus software on mobile devices. – NH. – 2017-06-21T16:57:08.187
1for better understanding: So this means, that taskmanager shows for example 0% CPU usage in overall ( all processes 0% ), but it could be that there is a hidden process that uses CPU, but I don't see it in taskmanager ? – user1344545 – 2014-02-08T04:16:25.893
I agree with Jonathan answer. – Calculating Machine – 2014-02-08T04:17:50.690
The task manager will always show a process called "System Idle Process" that runs during CPU idle time, that will appear to max out your CPU usage. It doesn't actually, and is not a virus. But yes, a virus can attach itself to taskman to hide its CPU usage. – Jonathan Baldwin – 2014-02-08T14:23:50.630