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 security software vendor VirnetX Holding (AMEX: VHC) climbed as much as 11.4% over last night's closing price on triple the average trading volume, following a sharp volume spike yesterday with a smaller effect on share prices.

So what: When I pricked up my ears to listen for significant VirnetX news to explain this move, I was overwhelmed by the swooshing of tumbleweeds and chirping of crickets. The company is due to report earnings in two weeks, which should be very interesting, but there's absolutely nothing going on today.

Now what: VirnetX has nearly tripled over the last year amid a rash of buyouts in the data security industry. It's easy to get carried away with a stock like this, and the speculative swings are only magnified by a sizable legion of short-sellers. VirnetX has its virtues, including some success in the patent-protecting courtroom arena and a still-reasonable P/E of 19 times trailing earnings, but inexplicable moves like this one makes me nervous about the stock's long-term health.

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