Is tracking employee's computer legal?

The situation is as follows. In our office, we decided to put an employee monitoring system on every computer. For the purpose of " advertising ", I will not say the name, but I will list the main features:

• Taking screenshots
• Monitoring running processes
• Monitoring open websites
• Interception of ICQ and MSN Messenger messages
• USB device monitoring
• Record start and end time
• Report Wizard - User Activity Analysis
• Remote installation and removal of agents
• Invisible agent mode