The U.S. Securities and Exchange Commission (SEC) suspended trading today in 128 inactive penny stock companies, including some Canadian firms, to prevent these stocks’ use in future pump-and-dump schemes.

Over the past few years, the SEC has been trying to thwart microcap fraud at the source by suspending dormant shell companies en masse, to avoid them being used in market abuse schemes. Since 2012, Operation Shell-Expel has seen more than 800 microcap stocks suspended by the commission in order to make them useless to scam artists.

The SEC says that the latest round of trading suspensions identified dormant shell companies in 24 U.S. states and Canada. Its Office of Market Intelligence scours the over-the-counter marketplace and identify shell companies that are ripe for abuse in stock-market scams.

After being suspended, a company cannot be relisted unless it provides updated financial information to prove it is a functioning company. The SEC says it is “extremely rare” for a company to fulfill this requirement.

“Operation Shell-Expel continues to be an efficient way to combat microcap fraud by denying fraudsters the empty nests they need to hatch their schemes,” said Andrew Ceresney, director of the SEC enforcement division. “We are getting increasingly aggressive and adept at ridding the microcap marketplace of dormant shells within a year of the companies becoming inactive.”