Data Execution Prevention (DEP) is a set of hardware and software technologies that help prevent damage from malicious software that attack your computer by executing arbitrary code from memory locations due to software vulnerabilities. DEP works by making sure that software uses system memory safely, blocking a technique used by hackers to exploit software vulnerabilities and install malware.

In a nut shell, DEP software works alone or with compatible microprocessors (Intel and AMD) to mark memory locations as “non-executable”. If a program attempts to write code and execute it from a protected location, DEP closes the program and notifies you. The software-only version of DEP is not as effective as the hardware version. Yet, it’s strongly recommended to turn it on.

By default, DEP is turned off for Internet Explorer in Vista. If DEP is so powerful, why is it disabled for important applications such as Internet Explorer? Well, the answer is simple. Microsoft disabled DEP to maintain backward compatibility with other plug-ins and add-ons that simply do not work with DEP. For example, until recently, even plug-ins such as Adobe Acrobat Reader and Flash Player did not work if DEP was turned on.

To enable DEP in IE7, right-click on the IE7 executable and select “Run as administrator”. If you don’t run this as an Administrator, the option will be greyed out. In IE7, click on the Tools menu and select Internet Options. On the Advanced tab, scroll down and check the option “Enable memory protection to help mitigate online attacks”. Click the Apply button and restart Internet Explorer if it was open.

Do you really need a DEP-enabled IE7? There’s not an answer to that question yet. It’s just trial and error. Work for a while with DEP turned-on and make sure everything works smoothly. If you experience issues with some specific plug-ins, contact the vendor for an updated version. As a last resort, you may need to turn off DEP for IE.