Unfortunately those DDNS services became all on payment, if not they will work for 30 days only, and after you have to confirm renovation by email. I love ASUS routers because you add any available DDNS and press save button, yes that's all! DO you want "mycomanyname.asuscomm.com"? if not already taken, please.. it's yours!
Sorry but I don't mind about attacks, there is nothing to attack, and who may guess that I have a router asus and I use its DDNS may aleady found my IP too, it's easier than guess.
DDNS is useful for me, to connect by VNC for example, videosurveillance, ecc. It should not be compulsory, who loves to have a "impossible to remember" string is welcome, but let me please chose