How does alert detection work in Microsoft Security Essentials?
When potential harmful content is detected on your computer, then Microsoft Security Essentials will display a window with brief instructions about the file, infection name, and possible actions like:
Based on your input, MSE takes the necessary steps in removing or leaving the file in its place. This is the only way MSE alerts you about a possible infection.
For more information access the following URL: http://windows.microsoft.com/en-us/windows/what-should-i-do-if-microsoft-security-essentials-detects-malicious-software-on-my-pc