SEC officials said on Feb. 8 that the firms involved -- none of which are household names -- have been the subject of repeated spam efforts meant to drive up trading of their securities and, subsequently, the value of the companies themselves.

The trading bans will last for 10 days, after which shares in the involved companies will be unlocked -- unless the SEC's ongoing investigation proves any of the firms were involved in the e-mail schemes.

While the ban might seem unfair to the businesses involved, especially if their names and securities were merely selected by scammers looking for penny stocks to inflate in so-called pump-and-dump operations, SEC officials said that in each business's case, there were sufficient questions raised regarding the "adequacy and accuracy" of information being advertised about the companies.

Criminals have increasingly begun using spam to drive up interest in cheap stocks over the last several years. Before sending out mass messages about a specific firm, the individuals buy stock in the companies in the expectation that, with their e-mails, they can convince other people to purchase shares. When prices of the shares involved rise, the schemers sell off their own holdings, thus the pump-and-dump moniker.

The spam messages, which often feature subject lines such as "Fast Money," have become one of the types of unwanted e-mail most frequently delivered to inboxes over the last year, alongside advertisements for prescription medications.