I thought that Defender checked your hard disk and sent information to MS about you if you had downloaded MTK and then kicked you out of the insider program. And then turned on your camera to see your reaction and sent it to the NSA. I read it in some forum somewhere.
I've been using it since 2009 when they released security essentials and I've not felt any need to replace it. I also have malwarebytes as a passive scanner though. Just keep your software updated and be mindful of what you click and you will be fine.
I've done some malware tests for graduation work purposes ~7 months ago comparing Win Defender, MS Essentials and Bitdefender IS (the last one just for curiosity). Guess which won Voted Spoiler WD not enogh and a security suite is essential
KIS 2015 gives me complete satisfaction, thanks to its efficiency and discretion. It also allows me to neutralize Difender and MS Firewall. That one "eats" my Credit Data at breakneck speed. The Kaspersky's price is reasonable in my country, unlike Windows ...
WD not enough and a security suite is essential, besides it's part of the spying machinery of Windows. murphy78 talks about it:
A third party firewall is a power user tool, not an essential piece of security software. The Windows firewall is solid and trustworthy. While people can argue about the Microsoft Security Essentials/Windows Defender virus detection rate, the Windows firewall does just as good a job of blocking incoming connections as other firewalls.
I think KIS also acts as a firewall. Why have two, especially that of MS "puts his nose" in all my stuff?
I haven't got virus or malware since like 5 - 6 years and im just using WD and i do scan with malwarebytes from time to time if you are smart enough and you what you are doing on the net WD is enough but if you dumb and you gonna download crap from unknown sources you and visit suspicious sites maybe need aftermarket AV and BTW adblockers helps to increase your security i prefer Ublock origin its light on the resource and dont slowdown browser or hog ram
WD was never enough, a faint tentative by MS --- it blocked keygens but nothing else, had virus because it wasn't efficient, switched to panda antivirus