An issue with your computer is blocking the VAC system. You cannot play on secure servers.

After taking sometime to recognize your issue and a very common one with steam it seems. I've come to the point of realizing that there are certain programs that do in fact alter the games ability to scan servers.

A small list of programs causing the issue. If you have gone to casual servers where custom textures or skins are applied to your gaming experience. Those in fact have sometimes a conflicting interest for some computer systems.  Not all systems run the same nor do they respond the same. Its always a good idea to check step by step when diagnosing your system.

For more information Visit the link provided below on steps to help correct the situation.

https://support.steampowered.com/kb_article.php?ref=2117-ILZV-2837

Before you resort to that let me research a few things k

I did all of that! i followed all those steps.
I;ve come to the conclusion that it's just a windows 10 and windows 8 issue.

i'm going to try and install windows xp and see what happens cause i get the same problem with
windows 7, Ubuntu n mac os x..

Restore Boot Settings to Default

Kernel Integrity checks, Kernel Debugging, and 
Data Execution Prevention (DEP) must be set to default to play on VAC secured servers. 
To change these settings to default please follow the steps below:
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• Exit Steam.
  
  
  
  
• Click the Start button, then 'All Programs', and 'Accessories'
  
  
  
  
• Right-click on Command Prompt and click "Run as administrator..."
  Note:If you are running Windows 8 you will need to press Windows Key + X and select Command Prompt (Admin)
  
  
  
• In the command prompt, type the following commands and press Enter after each command:
  
  bcdedit /deletevalue nointegritychecks 
  bcdedit /deletevalue loadoptions 
  bcdedit /debug off 
  bcdedit /deletevalue nx  
   
  Note:If you recieve the following error when entering these commands they are already set to default.The value is protected by Secure Boot policy and cannot be modified or deleted.
  

• Restart your computer.
  
  
  
• Launch Steam and test the issue again. 
  
  

An issue with your computer is blocking the VAC system. You cannot play on secure servers.

Well i can't play on secured servers.
I've been having this issue for about 10 months now! I don't know what the problem is.
I have followed this Valve Thread down to the T and nothing. https://support.steampowered.com/kb_article.php?ref=2117-ILZV-2837