I never seen any malware installing ddg as the default page, but I've seen many installing startpage. Also commercial softwares with default checkbox. I cleaned one just some days ago on my girl's laptop.

Sorry, I have no way to know if you are a victim or a bad actor in the matter, but I choose to ban you from anything I touch. And I know every geeks around me do the same.

If you are indeed a victim, I'm sorry for you and hope you'll find a way to get your legitimacy back. Right now it's very bad.