Its name is Towelroot made by geohot.
I hope it works for you because it worked for me (Im using a GT-N5100)! It was originally for the AT&T And Verizon Galaxy S5 but it should work with any kernel created before June 3
To download the apk, tap on the icon and it will automatically start downloading.
Anti virus apps will of course scan it as malware, don't worry, its a false alarm
And don't worry, it won't trip the Knox Counter
I suggest that you donate to geohot because, this app is awsome! And Geohot may have worked hours on this, maybe even days or weeks!