Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of cybersecurity company FireEye (NASDAQ:FEYE) jumped by more than 10% on Thursday after the company reported its fourth-quarter earnings, beating analyst estimates for both revenue and earnings. By 12:40 on Thursday afternoon, FireEye was up just over 11%.

So what: FireEye's revenue grew by nearly 150% year-over-year during the fourth quarter to $143 million. During the full year, revenue grew a staggering 163% to $425 million. Billings during the fourth quarter rose to $213 million, beating the company's prior guidance.

Along with this rapid rise in revenue, FireEye's spending also increased dramatically. R&D spending rose 147% year-over-year during the fourth quarter, and sales and marketing expenses more than doubled. Combined with a decline in gross margin during the quarter, this led FireEye's operating loss to nearly double compared to the same quarter last year.

The company's net loss for the quarter was $0.72 per share, and for the full year the net loss was $3.12 per share. FireEye expects this to improve in 2015, guiding for a net loss of between $1.80 and $1.90 per share on billings growth of about 40%.

Now what: Cybersecurity is a rapidly growing market, and FireEye is right at the center of it. Growth is set to slow down, but only because FireEye has grown to a size where doubling revenue every year simply isn't possible.

FireEye's heavy spending should be a concern to investors. During 2014, the company posted a net loss of $443 million, with sales and marketing spending nearly equaling revenue. FireEye expects its losses to narrow this year, but these losses can't continue indefinitely. FireEye raised $444 million during 2014 though a secondary public offering, and its cash balance currently sits at roughly $400 million. At the current rate that the company is burning through cash, this will only last a few years.

FireEye trades at around 14 times 2014 sales, and with growth slowing and massive losses piling up, the company looks like a very risky investment.

Timothy Green has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.