my kids spend a lot of time at the computer. I can't understand that they're doing so much there.

Have you tried talking to your kids? Maybe they can tell you what they're doing.

Children's safety is important. Computers, unfortunately, are not only useful. On the Internet there are many programs that are covered with beautiful pictures. The kids are curious. They're watching pictures. How this can end is not always clear. I recommend you install a keylogger computer https://www.refog.com/keylogger.html. This way you can keep track of all the sites your kids visit, and who they can communicate with and what they can talk about.