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What is the difference between - Windows Defender and Microsoft Security Essentials?

Should I run both?

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migrated from Nov 15 '09 at 15:04

This question came from our site for system and network administrators.

up vote 12 down vote accepted

A comparison of the difference between the two from Microsoft:

Q: How is this different from Windows Defender?

A: Windows Defender detects and removes known spyware only. It is not designed to protect against the full breadth of malicious software, and specifically does not prevent viruses, worms, Trojans, and other malicious software from infecting your machine. The new no-cost solution will be a comprehensive anti-malware solution.

Q: Is Microsoft Security Essentials designed to replace Windows Defender?

A: No but if you are running Microsoft Security Essentials, you do not need to run Windows Defender. Microsoft Security Essentials is designed to disable Windows Defender in order to manage the PC’s real-time protection, including anti-virus, rootkits, Trojans and spyware.

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Typical Microsoft gibberish. It wasn't designed to replace Windows Defender -- it just happens to do so. – duffbeer703 Nov 15 '09 at 15:01
If Security Essentials was designed to replace Windows Defender then it would be distributed with Windows, instead of being a separate download. To fully replace something it's not enough just to do the same stuff (or a superset) you must also take its place completely. In this case, being distributed alongside the OS. And that's what Security Essentials clearly doesn't do. – Joey Nov 15 '09 at 23:36
MS distributes MSE separately to fend off whining AV software vendors and possible lawsuits similar to the ones waged against IE. It does replace it, MS just puts in gibberish to sound like it does not, to keep the peace. – Moab Feb 17 '11 at 20:54

Microsoft Security Essentials is antimalware software, which means that it's designed to detect and help protect your computer against a wide range of malicious software, including viruses, spyware, and other potentially unwanted software.


Windows Defender, which is automatically installed with your Windows operating system, is software that detects and stops spyware. To learn more about Windows Defender, visit the Windows Defender Web site.


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