I'm just asking on which websites you get these pop ups. If it's only when you use NSC, it suggests a problem with this site rather than with your phone. Lots of others are today reporting pop ups when accessing NSC. I'm getting lots, but Chrome blocks them all for me.
Does it occur on sites other than NSC? Every time I go to NSC today I get multiple pop ups being blocked by my phone. No viruses here.
If you do actually have a virus you can always factory reset your phone. Just make sure to back up anything you need first.