Image source: VASCO.

What: Shares of VASCO Data Security International (NASDAQ:OSPN) rose 12.5% in April 2016, according to data from S&P Global Market Intelligence. The data security expert reported solid earnings on April 28.

So what: VASCO's first-quarter report revealed a positive surprise on the bottom line despite soft top-line sales. Earnings fell 59% year over year, but analysts had expected an 82% earnings plunge. The report lifted VASCO's shares 2% higher on April 29, the last trading day of the month.

Earlier, the stock rose 3.7% overnight on two separate occasions, but for no obvious reasons. Otherwise, April was a quiet month for VDSI with few splashy headlines and only a handful of sizable moves. It was 1.5% up here, 0.7% down there, and simply more of the small rises than small drops. Even the trading volumes were low.

In short, it looks like investors are getting over some of their qualms regarding VASCO's future. As a reminder, the stock's negative trend started in July 2015, when shares fell 23% in a single day after the company set its full-year guidance targets far below analysts' expectations -- and disclosed an internal investigation into alleged sales to Iranian businesses. Though US-Iranian relations may have improved in recent years, the Middle Eastern nation is still subject to heavy trade sanctions, especially on items like VASCO's data security products.

Now what: The quietly powerful April performance added to big gains in February and March. Between Feb. 10 and May 2, the stock gained 36%. However, that was more of a bounce off a deep bottom than a triumphant rise to the stars. VASCO's shares are currently trading 35% below their year-ago prices, and a painful 53% below last June's 52-week highs.

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.

VASCO's revenue has plunged since that fateful report, alongside operating margins and bottom-line earnings. It will have a lot to prove in coming quarterly reports, and I still haven't seen any closure on the Iranian sanction-breaking scandal.

May has not started out well for the security expert; its shares fell more than 6% in just five trading days. So April's bounce may not be sustained this month.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.