Major US ISPs (Comcast, AT&T) should detect clearly suspicious activity coming from customer IPs and warn them to scan their computers, check their TV apps, and find whatever is turning their internet into a proxy. It's very bad for the customers too (slows things down, gets their IP banned, etc)
Is there incentive for them to? If anything, you might be paying extra for the data use and not even know it, right? They would lose money