Making sure laid-off workers don’t walk off with more than they’re supposed to has become a growing security issue lately as tens of thousands of financial sector employees lose their jobs. The list of recent layoffs is long. Well-known alternative-asset management firms that have trimmed their workforces include London-based GLG Partners (100 layoffs) and Gartmore Capital (70); Chicago-based Citadel Investment Group (40); New York’s Highbridge Capital Management (35); and Dallas-based Highland Capital Management (30), which closed two funds.