Ensuring that your sources are legitimate is a massive part of your success and reputation as a journalist. There are so many accounts of lousy reporting, fake news, and illegitimate sources these days, so you must share with the interviewer what you do to avoid this embarrassing mistake from happening to you.
"One of my fast and firm rules is that I never allow for the use of anonymous sources. This rule has saved me from many embarrassing instances where I could have irresponsibly reported fake news. If I have to grant anonymity to a source, there is a lot of due diligence that must occur first."
"I always as myself if a source is credible and knowledgable before I lean on them for anything. Also, I make sure that my editors are on board and fully satisfied that my source is reliable. This decision isn't a one-person decision most of the time. Everything from a source is pre-verified before any publication or broadcast."