What Is Data Execution Prevention(DEP) And How To Disable It In Windows 7 / Vista

What is DEP ?

In Microsoft’s own words,

Data Execution Prevention (DEP) is a security feature that can help prevent damage to your computer from viruses and other security threats. Harmful programs can try to attack Windows by attempting to run (also known as execute) code from system memory locations reserved for Windows and other authorized programs. These types of attacks can harm your programs and files.

DEP can help protect your computer by monitoring your programs to make sure that they use system memory safely. If DEP notices a program on your computer using memory incorrectly, it closes the program and notifies you.

Why disable DEP ?

I was running multiple processes on different tabs in Firefox 3,  finally my Firefox crashed and Microsoft gave a very beautiful reason for the crash which you have read above. Actually it happened the moment I clicked on a YouTube video, it sounds weird, right? If you are a heavy geek like me, who works on multiple Firefox tabs and also use online services that need to access your system memory, then your Firefox is definitely going to crash unless you don’t disable DEP. Another reason to disable it is when it does not allow you to open Executable files that needs to access your system memory.

Note: Only disable DEP if your executable file is not getting installed or if your Firefox is crashing all the time(and Microsoft keeps giving DEP excuse).

How to disable DEP ?

Go to Start, right click on Computer and finally click on Properties. Now in the System window click on Advanced System Settings in the left sidebar as shown in the screenshot below.

Now in the System Properties Windows, under Performance click Settings as shown in the screenshot below.

Finally in the Performance Options windows, navigate to Data Execution Prevention tab and select the second option “Turn on DEP for all programs and services except those I select:” as shown in the screenshot below.

Now suppose you have to disable DEP for some executable file, just click on Add, and then select the file to add it in the list and you are done.

Well you can’t add Firefox because it is not an executable file, but it pretty much solved my problem.

Alternative Method – Disabling DEP completely from Command Prompt

Warning: Do not use this option if you are not an administrator. Make sure that you fully understand what you are doing.

From the Start menu, select All Programs, then go to Accessories and then finally right-click on Command Prompt and click Run as Administrator.

Once the command prompt is open, you can now disable the DEP by entering the following command line.

bcdedit.exe /set {current} nx AlwaysOff

Keep the Command Prompt open and run the executable file that DEP was preventing from running before. After you are done with the installation, simple type this command line to enable DEP back on again.

bcdedit.exe /set {current} nx AlwaysOn

If you want to completely disable DEP then you will have to remove “{current}” from the command line.

bcdedit.exe /set nx AlwaysOff

And to enable it back,

bcdedit.exe /set nx AlwaysOn

After you execute using the command prompt, the options from Data Execution Prevention tab in Performance options will vanish.

You can use OptIn and OptOut to give it a purpose,

OptIn – Enables DEP only for operating system components, including the Windows kernel and drivers.

bcdedit.exe /set nx OptIn

OptOut - Enables DEP for the operating system and all processes, including the Windows kernel and drivers. However, administrators can disable DEP on selected executable files by using System in Control Panel.

bcdedit.exe /set nx OptOut

Recommendation: I would recommend that you try the first method, if it fails, then you can try this second method(command prompt method) only if you are an expert user.

Comments, Questions, and Suggestion, all are welcome in the comments