Plaintiffs lawyers are slapping public companies with securities class actions months or years after the date the alleged fraud came to light as they turn their attention from cases related to the financial meltdown back to traditional securities suits.

The delayed filings are a shift from the previously common practice of pursuing a securities fraud class action days or a handful of weeks after a stock-price decline caused investor losses. Eight of the 23 securities class actions filed against public companies in October and November define the class as investors who bought or acquired the company’s stock during some time between 2006 and the first half of 2009. One has already been voluntarily dismissed by the plaintiffs. These cases are listed on Stanford Law School’s Securities Class Action Clearinghouse.