Does hallow/crimson/corruption spread throug walls to blocks?

[John tha noob]

I wanted to make a hallow artificial biome to farm souls of light and i was worried of my world getting hallowed without me knowing so the question is ¿does hallow/crimson/corruption spread throug walls and then to blolcks? please help me

 

[amenyoussef]

yes they can ,and they even can spread thorugh vines and thorny bushes