While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of FireEye (NASDAQ:FEYE) popped 4% in this morning after Barclays upgraded the cybersecurity technologist from equalweight to overweight.

So what: Along with the upgrade, analyst Raimo Lenschow planted a price target of $40 on the stock, representing about 24% worth of upside to yesterday's close. So while momentum traders might be turned off by FireEye's sharp pullback in recent months, Lenschow's call could reflect a sense on Wall Street that the company's growth prospects are now too cheap to pass up.

Now what: According to Barclays, FireEye's risk/reward trade-off is rather attractive at this point. "FireEye continues to be one of the most disruptive technology names with its differentiated, virtual-machine based approach to security," said Lenschow. "We believe the recent pullback among high valuation stocks has created a more compelling buying opportunity for long term-investors and as such we are increasing our rating to OW but taking a more conservative approach with our price target and lowering to $40 (from $50), based on a CY15 EV/Sales of 10x." When you couple FireEye's beaten-down stock price with its cash-rich balance sheet, the downside certainly seems limited enough to bet on those prospects. 

Brian Pacampara 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.