Popup from Lasrv.maha-media.com w/Fake Security Warning

I'm getting popup pages from Iasrv.maha-media.com (seems to be related to engine.spotscenered.info in my history) in Google Chrome pretending to be a Windows warning telling me that all my logins (FB, email, etc.) are potentially compromised and my system will be shutdown and locked if I don't call a number (didn't write it down). These are pretty urgent sounding messages that I know aren't legit but are still scary. I'm NOT clicking on any links or calling anyone but am concerned that my Norton Security isn't catching this. I scan regularly, use Win 7, but I did download Adaware anti-spyware recently although I've done this before without issue on other browsers. I've uninstalled it. There are no other suspicious programs listed in my control panel/programs installed. 

I use Chrome, have the latest version-Version 57.0.2987.133 but it is updating as I write this-and alternately use Firefox version 53.0.2. I don't click on weird links, go to porn sites or open unknown sender emails. I have not gotten any Norton warnings about sites lately. 

How do I get this off my computer? How did it get on here? Why isn't Norton catching it? 

Anyone with ideas about removing this? I don't even know how I got it. 

 

Thanks for any and all help! I'm sure I'm not the only one with this issue.