

There are options in the “Applications” section of the CCleaner computer cleaning tool to clean MS AntiMalware, which I believe means that when selected, CCleaner may delete information that confuses MSE. If the status remains Unprotected or the scans never complete, then I’d absolutely have you take the appropriate steps to remove malware from your machine, as well as uninstalling and re-installing MSE. Because that is exactly what you’ve been doing and it still returns Microsoft Security Essentials (MSE) to it’s green/Protected state, my opinion is that this is not the case for you. On the other hand, it’s also better to be safe than sorry, so running up-to-date anti-malware scans might be the first thing to do. Based on how often I see this symptom on clean machines (including my own), I’m skeptical that this is the case. Yes, there’s a small possibility that this is a side effect of malware on your machine. More often than not, it’s actually one of the first two.

The malware definition database is out of date.“PC Status: Potentially unprotected” can actually happen for several different reasons: The warning that Microsoft Security Essentials (MSE) throws is actually less than helpful. Potentially Unprotected Could Mean Several Things

I’ve run into several theories about why this might happen.
