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 communications systems integrator Black Box (NASDAQ:BBOX) plunged 18% today after its fiscal second-quarter results and updated guidance for the second half of its fiscal year fell short of analyst expectations.

So what: With approximately 20% of its sales coming from the federal government, Black Box is in the eye of the storm when it comes to budgetary uncertainty. This month's 16-day government shutdown pushed back orders, one of the factors that forced the company to lower its full-year guidance for revenues to a range of $955 million to $965 million and between $2.00 and $2.10 for earnings per share. That guidance is down significantly from that supplied in July ($1 billion to $1.02 billion on revenues, $2.70 to $2.90 on EPS).

Now what: Black Box expects to face continuing headwinds in its government segment. President and CEO Michael McAndrew told investors and analysts on the earnings call that "since the [government] reopening on October 17, orders have not picked up to pre-July levels. For planning and guidance purposes, we consider our current run rate to be the new normal for the federal government in our product segments."

Prior to today's drop, Black Box shares were up more than 50% relative to their May 1 closing low. Given the adverse environment in which it operates, investors can expect the stock to remain under pressure in the near term; furthermore, it isn't cheap enough to attract deep-value enthusiasts. Investors with an interest in Black Box may wish to wait for a more attractive entry point. There is no hurry to jump now.

Fool contributor Alex Dumortier, CFA, has no position in any stocks mentioned; you can follow him on Twitter @longrunreturns. The Motley Fool has no position in any of the stocks mentioned, either. 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.