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It actually sped up the system a bit after installation, indicating that it may be more efficient than the built-in Microsoft Defender Antivirus, which runs by default but deactivates itself if a third-party antivirus program is installed. Kaspersky Security Cloud Free was the undisputed winner in the free categories, beating all rivals in passive, full-scan and quick-scan impacts. Kaspersky did have the second-lightest full-scan impact in the bunch, however. The lightest quick-scan impact among paid programs was held by Kaspersky Total Security at 22%, a percentage that was nearly twice as much as ESET's full-scan impact. That may be because ESET doesn't have a quick-scan option.
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Among paid antivirus programs, ESET was not the fastest in all three categories that we measured: passive system impact, full-scan system impact and quick-scan system impact.
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