2016 has not been kind to FireEye (MNDT) investors -- and 2015 wasn't much better. Over the past six weeks, FireEye stock is down 39%, part of a long, long slide that has seen the "threat forensics" and malware protection firm lose 66% of its market cap. But at long last, relief may be at hand...

At least, according to BTIG Research, it might.

The news
Bright and early Wednesday morning, BTIG announced a big upgrade for FireEye stock on the eve of the company's Q4 earnings announcement. Calling the stock a "compelling buying opportunity," BTIG argued FireEye stock that currently costs just $12 and change could easily go to $15 within a year.

That much we know from media reports on the upgrade. Now, here are a few things you might not know.

Thing No. 1: The numbers are already (mostly) in
FireEye recently narrowed its earnings forecast for Q4 2015, telling investors that it's likely to report $184 million to $185 million in revenue for the quarter, toward the low end of previous guidance. Billings, on the other hand, which are predictive of future revenue growth, will run from $256 million to $257 million -- toward the high end of guidance.

Operating cash flow for the quarter will be positive, and probably in the $8 million-ish range, yielding full-year operating cash flow of perhaps $36 million. If correct, this will be a big turnaround from 2014, in which FireEye's cash flow was negative $131 million.

Thing No. 2: Cash profits are in sight
That improvement in cash flow, plus a reduction in capital spending that sucks up the cash, could result in positive free cash flow (cash profits) for FireEye as early as this year.

BTIG's analysis suggests that capital spending "will grow by 'only' 20% in F15 (vs. ~130% in F14)." Accordingly, the analyst believes FireEye "is on the cusp of giving investors more of what they're looking for in this environment: better revenue visibility, tighter cost control, and positive cash flow."

Thing No. 3: BTIG could be right
BTIG's big argument in favor of buying FireEye ahead of earnings goes like this: Historically, FireEye has rushed headlong in search of "growth at all costs." Now, the company is making moves aimed at securing "greater stability and (more importantly) generating free cash flow."

To BTIG's mind, that's good news for investors, and according to our data here at Motley Fool CAPS, BTIG has a record of being right about such things. While we haven't received good data on BTIG's recommendations for a while, our most recent CAPS snapshot of the analyst's performance, which dates to 2014, shows BTIG outperforming 75% of the investors we track, and getting most of its recommendations right. Best of all, the average BTIG recommendation we have on record is beating the market by 19 percentage points!

And one more thing...
All that being said, FireEye is not a stock for the weak of heart. Investors need to be aware that the stock has never reported a GAAP profit. Furthermore, data from S&P Global Market Intelligence (formerly known as S&P Capital IQ) show that FireEye only generated full-year positive free cash flow twice in its history.

Yes, 2016 could be the year FireEye turns things around and begins generating real cash profit for its shareholders. We'll get a better read on that when earnings come out tomorrow. Should the news be bad, however, investors desiring to invest in the Internet security space might consider an investment in FireEye rival Palo Alto Networks (PANW -0.26%) instead.

Like FireEye, Palo Alto Networks is not currently profitable. Unlike FireEye, Palo Alto Networks has already achieved the goal of reaching free cash flow profitability. Over the past year, the $375 million in cash profit generated at Palo Alto gives the stock a price-to-free-cash-flow ratio of less than 28. (Factor in net cash, and the enterprise value-to-free-cash-flow ratio is even cheaper).

What's more, analysts who follow the stock forecast a blistering pace of 46% annual profits growth for Palo Alto Networks over the next five years. That's twice the rate of growth forecast for FireEye.

Long story short, whatever happens at FireEye tomorrow, investors' best move might be to buy Palo Alto Networks instead.