I installed the Kingo Root (aka KingoRoot) APK on my Android device and launched the app. My phone was on airplane mode and I saw the screen
Kingo ROOT
Please make sure your network connection is stable and try again.
What exactly beyond the app itself does the app need to root the device that requires network access?
Not sure entirely, but this may be the reason why
KingoRoot was banned from the XDA Developers forum along with vRoot in November 2013 due to concerns with the information collected by the app during the rooting process.
Ragnar (Retired Forum Moderator) Nov 6, 2013 at 3:02 PM
Be aware that as of this moment XDA has deemed the Kingo root method and Vroot method are not allowed on XDA. There are concerns with the information which is collected during the root method by the exploit. It is not about a continuous malware which may affect your device but about important information shared about your device, serial numbers etc during the root process which could be huge securities issues.
You have all been warned
Thread closed. If you have any questions regarding this please contact myself or any other moderator via PM
Another suggestion is server access is needed to cross reference your device to a list of possible exploits that can be employed on it...
Kingo root download exploit from their server
https://www.quora.com/What-things-exactly-does-Kingo-Root-do-for-rooting
And this guy highlights a bunch of app permissions, bolding the privacy oriented ones for offloading user data to a remote server
it has its own service running in background which maybe pushing your data to their servers