Fortinet stock is up 14 percent today after the security vendor reported sunny fourth-quarter earnings.

Fourth-quarter revenues of $362.8 million beat the company's own forecast of $341 million to $347 million.

More importantly, bookings in the fourth quarter — a reflection of probable revenues to come — were $463.4 million, higher than the company's earlier prediction of $424 million to $432 million.

The company expects first-quarter revenues to be $330 million to $335 million, which would be an increase of about 17 percent compared with the same quarter a year ago.

The positive earnings report contrasts with the disappointing third-quarter earnings of a few months ago. What happened in between? One possibility is that Fortinet benefitted from a renewed focus on smaller enterprises and managed service providers, "customers where they perform well," analyst Catherine Trebnick of Dougherty & Co. wrote in a research note issued prior to Fortinet's earnings.

Fortinet credited its bounceback to its efforts to boost sales productivity and cut expenses, noting that those programs aren't yet complete. "It feels like the engine is more in place, but there's probably still, quite honestly, some work to do there," said Fortinet CFO Drew Del Matto during yesterday's conference call with investors.

Fortinet's fourth-quarter net income was $25.2 million, or 14 cents per share, compared with $32.2 million, or 18 cents per share, in the same quarter a year ago.

Non-GAAP earnings per share of 30 cents per share beat the analyst consensus of 21 cents, according to Thomson Reuters.