TripAdvisor borrows anti-fraud techniques from finance industry "Our popularity index is our ranking of what TripAdvisor's users think are the best places," said Adam Medros, the firm's head of product development. Ultimately, higher in that index means more exposure for businesses, so there's certainly incentives to try to manipulate it, either by raising yourself up or knocking others down. The precise details of the "signals" it measures are a closely-guarded secret, but include comparisons with other authors and reviews. The connections are mapped out visually in software that TripAdvisor says makes it more "intuitive" for its human investigators to spot suspicious patterns. "If I'm a user interacting on TripAdvisor I'm not going to be connected to 13 other people who are reviewing the same sequence of properties in the same time frame," said Andrew Marane, TripAdvisor's head of content integrity and a former fraud investigator in law enforcement and for e-commerce operations. While how we do it is a mystery, which is the biggest advantage we have in fraud detection, but the resources we put behind it aren't a mystery and they're significant. We put everything into one of three buckets: if it's obviously stinky we remove it, if it's obviously good we wave it through and it's usually on the site within 24 hours. It's the 'questionable' stuff in the middle bucket where you're not immediately sure and we put more resources. The biggest challenge is finding the fraud without impacting the good users. It's just as bad removing a good review that someone spent time on as it is letting a bad one through. This is the tightrope we have to walk. An average of about 13,000 reviews fall into the questionable category every day, although not all are due to potential fraud. "The team goes and looks at it and works out if someone has developed a new trick," said Medros. In any kind of fraud you have people who are continually innovating and trying to reverse engineer what you're doing to catch them. The algorithm certainly doesn't learn as fast as a very intuitive and inquisitive investigator does. That team is always trying to stay one step ahead.