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 (MNDT) 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.