When controversies about Facebook started making the news recently, staffers at CNNMoney knew quickly it was a topic their audience was very interested in.

How?

A tool they built told them.

"We knew that they were hungry for that," said Leezel Tanglao, assistant managing editor of programming, "and we saw it surging."

That notice came from the proprietary tool, Social SURGE, which stands for "social unit of reach, growth and engagement." SURGE was built by a team at CNNMoney who were charged with creating a social metric that told staffers how their audience was reacting and interacting with content on Facebook.

The challenge, from Ed O’Keefe, a senior vice president at CNN, was to create an in-house tool to measure virality and reveal the types of stories that engage readers.

Tanglao brought in developer Helen Shen and senior data analyst Ally Tubis (who now works for an analytics firm) to tackle the problem. The result, a few months later, was SURGE, which measures engagement, sharing, liking and commenting for CNNMoney content on Facebook. O’Keefe oversees other verticals, including those focused on health, tech, politics and style, so there's potential that SURGE could expand elsewhere. CNN has also monetized SURGE, creating the opportunity for advertisers to sponsor popular stories.

"The stories move through a scale of what we call ‘virality,’ which we created ourselves internally," Tanglao said. "If and when a story reaches a certain level of virality on our scale, it will SURGE. Any visitor to CNNMoney can see when this is the case from the teal lighting bolts on our homepage."

By building in-house analytics, CNN is in-step with other news organizations, like BuzzFeed and Mashable, that have created proprietary tools to measure their audiences.

The success of the tool shows what can be done with a diverse team from different disciplines, Tanglao said. When they were first given the job of creating a tool to measure impact, they had no idea where to start.

"When you have the right key people in place and you have the idea and the goal of being really open-minded and flexible, you can create things," she said, "and this is definitely a testament to that."

Now, SURGE is one of the tools staff use to guide programming. When stories about controversies at Facebook surged, CNNMoney reacted with a Facebook Live discussion about the story. It is not, however, the only tool they use.

"We're always going to tell the important and good stories no matter what," Tanglao said. "Having a tool like this has really helped us hone in on our constant listening to our users."

The benefit, she said, is SURGE helps staff at CNNMoney get to know their audience better, including what platforms they're on and what they respond to.

"If you don't know who your audience is," she said, "then you're not really serving your audience."

Correction: A previous version of this story noted that CNNMoney recently monetized SURGE. That is incorrect, it was monetized shortly after launching. We apologize for the error.