Mining software is often blocked by antivirus software (including Windows Defender). This happenes due to the inability of antiviruses to distinguish between malicious / viral mining (when a trojan installs it without the user's knowledge) from a demanded one (when the user wants to install the miner himself). In most cases, antiviruses simply block everything related to mining, whether the user needs it or not without any investigation. Even if the miner is not blocked by your antivirus immediately, it can be blocked later. Therefore, before downloading and installing the miner we recommended to create a separate folder for it and add miner to the exceptions of your installed antiviruses (including Windows Defender). And only after that download the installer to the folder prepared for it and launch miner. Also, mining downloading can be blocked by the built-in antivirus of the browser, in which case you must press Ctrl + J in the browser and unblock the download in the window that appears.