A former FBI agent is using "cold-case" techniques to figure it out:
Gertjan Broek, a lead researcher with the Anne Frank House in Amsterdam, believes that the search for an informant might prevent researchers from discovering what really happened. “By asking ‘Who betrayed Anne Frank?’ you actually assume tunnel vision already. You leave out other options,” he says.
It’s possible, Broek says, the Franks weren’t betrayed at all—instead they might have been discovered by accident. There’s a chance that those in hiding were discovered during a search regarding fraudulent ration coupons, he says after a two-year research project.
Another group of more than 20 forensic, criminology, and data researchers hope to narrow the margins to a single culprit. The team, led by retired FBI agent Vincent Pankoke, is treating the investigation like a modern cold case. For years they’ve been combing through archives and interviewing sources around the world while also using 21st-century technology to crosscheck leads. The team has created a 3-D scan of Frank’s hiding place to see how sounds might have traveled to nearby buildings.
Regardless, it's fairly certain that Anne Frank was not a "Belieber."