Five years ago next week, the stock market experienced what became known as the “flash crash.”

The U.S. stock markets saw prices suddenly plunge on May 6, 2010, losing $862 billion of valuation in a matter of minutes. The rapid drop of 600 points spooked investors, even though that sudden drop was erased later in the day.

Today, even as the stock market bounces around record or near-record highs, last week’s arrest of a rogue trader in London accused by federal officials of causing the so-called flash crash of 2010 has investors raising questions about market manipulation and market vulnerability.

Pittsburgh native, billionaire investor and Shark Tank star Mark Cuban was quoted in USAToday saying what many people are thinking “If this one random guy could impact billions of market value in seconds or milliseconds, what’s going on?”

The unexplained flash crash worried investors and should have worried federal regulators. But those worries linger, five years after the event.

The flash crash was troubling. But equally troubling is the passage of five years between the event and charges being filed against Navinder Sing Sarao, the London trader accused of causing the flash crash. Cuban, along with some Wall Street insiders as well as average investors are increasingly concerned that technology has allowed rogue traders to get ahead of regulators.

Harsh critics of Wall Street, including Michael Lewis, author of a 2013 book about high-speed traders called “Flash Boys,”often allege that markets are “rigged.” That might be a bit too strong a statement, but there is a general feeling among many investors that the stock market is something of an insiders game — that the best deals go to the big investment banks and their wealthy clients.

In addition to fears expressed by Cuban, there is also the concern that this one London trader is not the only one playing the risky games that caused the flash crash.

Many investors burned by the 2007-08 market crash triggered by the mortgage meltdown have not returned to investing — or are only putting a toe in the markets, reluctant to see their life savings vulnerable to another sudden market decline.

Computer technologies used on Wall Street worry many investors as well as Washington regulators with high-speed traders using complex computer algorithms to conduct hundreds of stock trades in fractions of a second. Some high-speed traders know that they can profit executing trades a few nanoseconds ahead of others, so they place their trading computers in buildings next door to the stock exchange computers. Many of these traders profit from holding a stock for just a few seconds before selling in a flash.

But these business models are not about investing. They are ways of gaming the system and average investors see it as more insider profiteering.

If the stock markets are to remain credible, investors need confidence that the playing field is level and that a random computer bug or rogue trader won’t cause a market crash that wipes out life savings or causes a global economic meltdown.

To reassure investors, federal regulators need to get ahead of new technologies and shut down new ways of gaming the system. At this point, however, regulators seem to be playing catch up — and investors still eye the stock market warily.