When Microsoft Security Essentials detects a potential threat, it uses the associated definition file to assign an alert level to the threat. It then applies the default action associated with that threat level.

Alert levels help you choose how to respond to viruses, spyware, and other potentially unwanted software. While Security Essentials recommends that you remove all viruses and spyware, not all software that is flagged is malicious or unwanted. The information in this table can help you decide what to do if Security Essentials detects potentially unwanted software on your computer.

Alert level

What it means

What to do


These are widespread or exceptionally malicious programs, similar to viruses or worms, which negatively affect your privacy and the security of your computer, and can damage your computer.

Remove this software immediately.


These are programs that might collect your personal information and negatively affect your privacy or damage your computer. For example, the program collects information or changes settings, typically without your knowledge or consent.

Remove this software immediately.


These are programs that might affect your privacy or make changes to your computer that could negatively impact your computing experience. For example, the program collects personal information or changes settings.

Review the alert details to see why the software was detected. If you do not like what the software does or if you do not recognize and trust the publisher, consider blocking or removing the software.


This is potentially unwanted software that might collect information about you or your computer or might change how your computer works. However, the software is operating in agreement with licensing terms displayed when you installed the software.

This software is typically benign when it runs on your computer, unless it was installed without your knowledge. If you're not sure whether to allow it, review the alert details, or check to see if you recognize and trust the software publisher.

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