What happened

Another hike to the benchmark federal funds interest rate is coming -- and growth investors are nervous.

According to experts polled by CNBC, chances are good that when Federal Reserve officials announce their decision on interest rates Wednesday, the hike will be a relatively benign 25 basis points (0.25 percentage points). That would be down from the 0.5 percentage point hike it delivered in December, and the 0.75 percentage point it instituted in November. However, it would still push the target interest rate to 4.75%. Investors in growth stocks -- and cybersecurity stocks CrowdStrike Holdings (CRWD 2.30%), Fortinet (FTNT 0.46%), and Zscaler (ZS 1.04%) in particular -- aren't 100% certain they like the sound of that.

As of 11 a.m. ET Monday, CrowdStrike shares were down 2.7%, Fortinet was off by 2.8%, and Zscaler was leading the whole sector lower with a 3.1% decline.    

So what

Monday morning's price declines came on the heels of an analyst's downgrade for Fortinet on Friday that also pulled CrowdStrike lower. Citing "subdued" channel checks, Mizuho Bank's Gregg Moskowitz repeated warnings of a decline in IT spending among corporations cautious about a slowing economy. This week's Fed action could potentially heighten those concerns. 

Consider: The share values of CrowdStrike and Zscaler, and to a (somewhat) lesser extent Fortinet, are based primarily on investors' hopes about what the companies will earn in the future -- i.e., their growth rates. Currently, neither CrowdStrike nor Zscaler are earning anything at all, and aren't even expected to begin earning GAAP profits before 2026 (CrowdStrike) or 2027 (Zscaler).

Fortinet is at least profitable now. But with the highest market capitalization of the three ($41.2 billion, or 55 times earnings), its valuation depends greatly on investors' confidence that it can grow earnings at the 24% annual rate that Wall Street expects. The valuations of CrowdStrike and Zscaler, meanwhile, depend on even more aggressive annual growth assumptions of 31.5% and 47.8%, respectively, according to data from S&P Global Market Intelligence.

Now what

But what if these companies don't grow as fast as they're supposed to? As the Fed steadily ratchets interest rates higher, making money more expensive to come by, and making it harder for cybersecurity firms' clients to afford security upgrades, their growth is likely to slow.  That, in turn, could lead investors to be unwilling to pay such high multiples for the profits that Fortinet is earning, or that CrowdStrike and Zscaler might (or might not) eventually earn.

This, in a nutshell, is what investors are wondering this week: Will the Federal Reserve really only raise the federal funds rate by the 0.25 percentage points that economists expect, or might the central bank keep trying more aggressively to drive a stake through the heart of inflation -- so to speak -- and raise interest rates by 0.5 percentage points again? For that matter, even if this hike is only 0.25 percentage points, what might the Fed signal about when it expects to raise rates again? And how many more times does the Fed intend to raise rates this year, and how much will that slow the U.S. economy's growth?

Until these questions are answered, there's extra risk involved in investing in growth stocks such as CrowdStrike, Zscaler, and Fortinet. Granted, investors could mitigate that risk by only buying the one company among those three that is both free-cash-flow positive and GAAP-profitable already: Fortinet.

But you can't eliminate the risk entirely -- and there's the rub.