How to remove dataloading.net? On my father's mac, dataloading.net keeps popping up in tabs. It doesn't seem to be in Safari's extensions (at least not visible in preferences). He has clean my mac 3 installed. Can this problem be solved with that? 

I'm having trouble recommending any virus scanner, because there's a lot of crapware out there.
If you suspect your Mac may have malware or adware installed on it, I would recommend trying BitDefender, a lightweight antivirus app for Mac (available for free on the Mac App Store), which I have found to be especially good at detecting both adware and malware and then removing it. BitDefender scans your machine when prompted (good for an ongoing issue) but does nothing in the background. 

If you want constant protection in the future (that promises to block this kind of adware/malware from being downloaded onto your Mac in the first place, and has fulfilled its promise twice for me) you can try Avast, which is also free (but not available from the Mac App Store, just their website). 

Hope this helps, let me know if this fixes the problem or not!