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 information security specialist VASCO Data Security International (Nasdaq: VDSI) look cracked today, falling as much as 15.8% on moderately heavy trading volume.

So what: VASCO's first-quarter earnings merely matched analyst targets rather than blowing them away, and the company stuck to its earlier full-year guidance. For a stock that doubled over the past seven months and gained 81% since the last earning report, that simply won't do. Only mind-blowing excellence could have satisfied Mr. Market at this point.

Now what: The IT security sector has been overheated since the buyout binge of last fall that culminated in Intel (Nasdaq: INTC) inexplicably buying McAfee. Corrections like this one are necessary to bring these stocks back to reality now that the acquisitive mood appears to have faded. In particular, online security expert VirnetX Holding (AMEX: VHC) had absolutely no business quintupling over the last 12 months and won't get any buyout offers until its valuation aligns with business reality. You have been warned.

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Fool contributor Anders Bylund holds no position in any of the companies discussed here. Intel is a Motley Fool Inside Value pick. VASCO Data Security International is a Motley Fool Stock Advisor selection. Intel is a Motley Fool Income Investor choice. The Fool owns shares of and has bought calls on Intel. Motley Fool Options has recommended a diagonal call position on Intel. 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 is investors writing for investors.