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I don't use one but a free one is AVG or you can check Kaspersky....I just use windows defender (leave it on don't really need to scan as it does its job by itself) (comes with stock windows 7) and run C-cleaner that's all. Firefox and Yandex have their own virus scan for downloads so you really don't need one in my opinion....as long as you have ad block installed, it catches all the pop ups and malware.....
The best add-on for any browser, it's free and blocks the annoying pop up ads and has a database of ads with malware to block and youtube video ads (before the actual video) I highly recommend it...
https://adblockplus.org/
The best add-on for any browser, it's free and blocks the annoying pop up ads and has a database of ads with malware to block and youtube video ads (before the actual video) I highly recommend it...
https://adblockplus.org/