Starting with Windows Internet Explorer 7 on Windows Vista, the Internet control panel item includes an Enable memory protection option to help mitigate online attacks. This option is also referred to as Data Execution Prevention (DEP) or No-Execute (NX). When this option is enabled, it works with the processor to help prevent buffer overflow attacks by blocking code execution from memory that is marked as non-executable.
In Windows Internet Explorer 8 on the Windows Vista with Service Pack 1 (SP1) operating system or a later version, this option is enabled by default. DEP/NX does not protect against all memory-based vulnerabilities. But when it is combined with other technologies like Address Space Layout Randomization (ASLR), it helps prevent common buffer overflow vulnerabilities in Windows Internet Explorer and the add-ons that it loads. No additional user interaction is required to provide this protection, and no new prompts are introduced.