I had a huge problem with viruses on the laptops. After playing detective for a couple of weeks, I figured out a couple of possible culprits:
1. Flash drives travelling to different computers;
2. Students installing various toolbars;
3. Students clicking on advertisements.
*Flash drives are now assigned to specific computers. Flash drives can be virus carriers and can contaminate other computers. If a virus shows, it is now contained to the computer and to the flash drive.
*Students are also assigned to specific computers. Because I share the laptop cart with other teachers and I can only check out 12 laptops. A group of 3 to 4 students are assigned to a numbered computer. They are responsible for happens on that computer and periodically I check the browser history.