Malware is the overarching name for applications and other code, like software, that Microsoft classifies more granularly as malicious software or unwanted software. Either no threats are found, or an application or software is categorized as malware or potentially unwanted software. Once enough data is gathered, Microsoft's security solutions can make a determination. Users can choose to download and run the application normally if they wish to. Warnings for unknown software aren't blocks. Not all uncommon programs are malicious, but the risk in the unknown category is much higher for the typical user. There's generally a delay from the time new malware is released until it's identified. Think of Unknown/Uncommonly downloaded warnings as an early warning system for potentially undetected malware. With almost 2 billion websites on the internet and software continuously updated and released, it's impossible to have information about every single site and program.

It takes time to identify and block malicious sites and applications, or trust newly released programs and certificates. No antivirus or protection technology is perfect. The following list may not be comprehensive, and Microsoft reserves the right to adjust, expand, and update these without prior notice or announcement. New forms of malware and potentially unwanted applications are being developed and distributed rapidly.

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