Ryan Corey remembers when his business plan would get him and his team laughed out of a room with potential investors. Back in 2015, when the Cybrary platform for cybersecurity learning was founded, it didn’t matter that Corey had amassed over 175,000 signups in six months.

Investors didn’t like his business model, based on attracting users with free lessons. And it probably didn’t help that his website was a work in progress. “When you give something away, they tend to cringe,” says Corey, the 39-year-old CEO. “And our look was so ugly. But users were using the crap out of it.”

Now, his company, Cybrary (that’s cyber library) has grown to more than 2.6 million users, with 2,000 new users a day. The company claims to offer thousands of hours of courses and hundreds of hands-on learning exercises in its catalog.

Those are numbers that investors can’t mock. Cybrary has landed $15 million in a Series B funding round. BuildGroup led the deal, with participation from Arthur Ventures and Gula Tech Adventures. As part of the deal, Gray Hall of BuildGroup and Ron Gula of Gula Tech join the company’s board of directors.

The College Park, Md.-based company will use the new round toward hiring more employees, adding more content and improving a network of creators and industry subject matter experts that have helped populate the platform with lessons and mentorship services, Corey says. The company has raised a total of $23 million to date.

Cybrary’s growth is perhaps partly owed to a boom in the cybersecurity field. Data breaches command headlines and can keep executives up at night. IBM and Ponemon Institute reported this year that breaches cost U.S. companies $8.19 million on average.

The U.S. Bureau of Labor Statistics expects job openings for information security analysts to grow 32 percent from 2018 to 2028, faster than the average for all occupations. And online jobs board Indeed reported that the U.S. saw a 7 percent increase in the share of cybersecurity job postings from 2017 to 2018. India saw a 40 percent jump.

Other companies have also seen an opportunity in the industry. Coding bootcamp Lambda School said it’d use a round of funding raised this year toward adding cybersecurity classes. And coding bootcamp Trilogy’s cybersecurity courses helped sell it as an acquisition for online program manager 2U in April.

More than 60 employees now make up Cybrary, Corey says. In particular, he wants to double the number of engineers on staff to 24 over the next two years.

The free version of Cybrary comes with introductory courses, syllabi, assessments and a live chat feature to help users. A premium license, which costs $99 per month, gives access to the entire course catalog, live online training, practice exams, scenario-based virtual labs and a mentor network.

The company also offers a service to train teams of employees for businesses, a package that includes analytics around how the team has progressed.

The platform’s content ranges from a single 10-minute course to a six-month program, where users are expected to commit 10 hours a week to prepare for jobs like network engineer and penetration tester.

Corey considers the experts network part of his company’s secret sauce. In a field like cybersecurity, having the most updated lessons is pivotal to pleasing customers. “That group of people is the most valuable thing to me,” he says.

About 1,700 experts make up a network of mentors, instructors and content creators. Course instructors are paid a one-time fee for content. Others sign up to access more Cybrary content or to build a reputation as an expert within cybersecurity.

Before he became a member of the mentor and instructor network, William Carlson started as a free user of Cybrary, which he came across while looking for ways to prepare for an information systems security professional certification exam.

Carlson, a 38-year-old IT and cybersecurity director in the Fort Worth area of Texas, says the exams require years of previous experience, cost hundreds of dollars and can last up to three hours. “I was not only looking to learn, but I wanted to know my blind spots—what did I know, and what didn’t I know,” he says.

He passed the exam on his first try and used Cybrary resources to gain certifications as an information security manager and payment card industry professional. Carlson decided to pay for a subscription for the virtual labs and mentor network, communicating with mentors through Slack and Zoom calls. He decided to join the expert network to help others who are uncertain about breaking into the industry.

Cybrary is not currently profitable, but is on its way, Corey says. He said competition isn’t much of a concern. Still, he’s open to acquiring another company. “If a piece of that network grows enough, we’d have to make a move.”