Yeah, internet browsers - you use one to go to websites - as that's pretty self-explanatory I'm not understanding the question.
The built-in one, Chrome, Firefox, and any others that re-installed automatically after the factory data reset because you used them before - go to apps management and clear data for each one that you have.
Otherwise, describe what you mean by malware being left behind after a factory data reset.
And I don't mean what is the definition of malware - I mean what malware do you have?