The Securities and Exchange Commission (SEC) over the last month has suspended trading on securities offered by 21 companies in reaction to market volatility caused by “apparent social media attempts to artificially inflate their stock price.”

Part of the continuing fallout related to January’s initial GameStop stock surge, the SEC vowed to monitor the market for unusual activity driven by retail investors trading tips and information about specific stocks on social media.

In a press release Friday, the agency announced it had temporarily halted trading on 15 companies, and earlier in February it suspended six others.

“We proactively monitor for suspicious trading activity tied to stock promotions on social media, and act quickly to stop that trading when appropriate to safeguard the public interest,” said Melissa Hodgman, acting director of the SEC’s Division of Enforcement, in the press release. “We also remind investors to exercise caution and do their diligence before investing generally, including in companies promoted on social media.”

In its order, the SEC said it suspended trading in the 15 companies because questions arose about their operating status—none had reported to the SEC with required financial information in over a year—and because of “recent, increased activity and volatility in trading in the securities of each of these issuers” driven in part by “certain social media accounts (that) may be engaged in a coordinated attempt to artificially influence their share prices.”

The moves by the agency appear to be part of a more aggressive stance to police valuation swings in stocks that are effectively dormant. Sudden market interest in stocks that have not traded much at all in the past year, haven’t issued financial statements, and haven’t met SEC reporting requirements are considered most susceptible to social media-driven volatility.

The SEC never halted trading on GameStop, even though its wild value swings in late January and early February were driven, in part, by retail investors touting the stock on social media.

However, trading on GameStop was halted for customers of several FinTech apps, including Robinhood Financial. Such halts are allowed under SEC rules.

According to Feb. 18 testimony by Robinhood Co-Founder and Co-CEO Vladimir Tenev to the House Committee on Financial Services, the platform halted trading in GameStop on Jan. 28 because it did not have enough collateral to cover the value of all the trades being made on the stock by its customers. Robinhood is required by the SEC’s T+2 settlement cycle to have enough collateral deposited with the clearinghouse to cover the value of stocks being traded over its platform for two days—from the time the sale is executed to when the sale is sent to a clearinghouse for clearance and settlement.

On Jan. 28, Robinhood’s collateral position increased from nearly $700 million to $3.7 billion, driven by the GameStop frenzy. Unable to cover a sudden $3 billion collateral call, Robinhood halted trading on the stock “to ensure that our customers could continue trading in the thousands of other stocks available on our platform that day and in the days ahead,” Tenev wrote.

Robinhood would eventually reopen trading on GameStop and secure $3.4 billion in investment from outside investors to help fulfill its collateral obligations with its clearinghouse.

In a January investor alert, the SEC described how broker-dealers like Robinhood “may determine not to accept orders where a transaction presents certain associated compliance or legal risks.”

In the same alert, the SEC described another way the market can limit trading on certain stocks. The national securities exchange and the Financial Industry Regulatory Authority (FINRA) have Limit Up-Limit Down rules in place “designed to prevent trades in these stocks from occurring outside a specified price band,” the alert said.

“This price band is set at a percentage level above and below the average price of the stock over the immediately preceding five-minute trading period. If a stock’s price moves outside these price bands for more than 15 seconds, trading in the stock will be paused for five minutes,” the alert said.

Reduced settlement cycle? Probably not

Will recent market volatility driven by retail investors make it more likely, or less likely, the SEC will revisit its T+2 settlement cycle rules?

Tenev said one way to prevent the trading stoppage on GameStop his company was forced to implement from happening again would be for the SEC to allow securities trades to be made in real time without its two-day settlement requirement and collateral obligations.

“The industry, Congress, regulators, and other stakeholders need to come together to deploy our intellectual capital and engineering resources to move to real-time settlement of U.S. equities,” Tenev wrote in his prepared testimony. “Accomplishing this won’t be without its well-documented challenges, but it is the right thing to do, and Robinhood is eager to drive this critical effort on behalf of all investors.”

In September 2017, the SEC reduced the settlement period from three days to two. At the time, Commissioner Kara Stein said the agency may consider further reducing the settlement cycle period. Although the SEC was scheduled to revisit its settlement cycle regulations three years after the reduction to two days, it never did.

Recent actions by the SEC and FINRA against Robinhood make it clear regulators are likely more interested in policing the FinTech’s alleged misdeeds than agreeing with its CEO to reduce T+2 settlement cycle rules.