Remove X_Pingback

Hi, everyone.

I am trying to remove the X_Pingback.

Because according to Sucuri, there are a lot of WordPress websites are being use to perform DDoS attacking.

Therefore, I want to find some workable code to remove the X_Pingback.

I applied quite a number of code which I found from Google / StackOverflow / WordPress support forum.

But no luck, X_Pingback still existing.

Does anyone here manage to remove the X_Pingback from WordPress version 4.4.2? Mind to share your code also please.

Thanks.