Those are the same ones I am talking about. They too are the result of bot infestations. A lot of times the porn site they refer you to is legitimately unaware that traffic is being routed to them illegally. They pay people for referrals and have no way of knowing what tactics the people taking advantage of their referral system used. Other times the porn sites are fully aware and paid specifically for that type of spam service. Such sites typically have systems set up in countries that don't like to cooperate with authorities and route their traffic through compromised systems that have no way of knowing they are being used for such purposes. There is a lot more to these operations than just one entity sending out spam from their own networks or even from compromised networks. Even if the spam sent you to a reputable porn company working within a country that does take such things seriously and not taking any precautions to hide the true owners, you need to prove the spam originated from them, otherwise the next great strategy for knocking out your competitors is to send spam that directs traffic to them and leads to their eventual arrest. There's a lot more to spam than you see in your inbox. I could go into greater detail, but all of this is out there for you to research if you are really interested.