Please provide more details on what you are looking to do... Is it just your MKTO database that has bad data, or is it also SFDC? Where do you see this bad data coming from? And what type of data - invalid leads, duplicates, etc.?
You'd most likely want a vendor that can do this for you but without more information I can't suggest anyone.
It was our bad data which we used for learning. We have manually cleared
the data. .