Horizon DataSys Inc. announced on Tuesday the release of Drive Vaccine, a cross-platform solution that provides security for PCs and Macs in hybrid environments. The company is targeting schools, libraries, government agencies and other organizations that employ mixed networks with multiple users for each machine. Drive Vaccine creates a write-protected area in the hard drive on each client computer and makes all changes, from deleting files to installing software, in a separate area, allowing the user to roll back the operating system upon restart and leave it the way it was for the next person. Each end-user license is US$39, with volume and educational discounts available. Drive Vaccine runs on Mac OS X, although Horizon DataSys does not note the minimum version required on its Web site.