Which of the following best summarizes the main idea of the passage?
Employees should be constantly warned about virus threats to ensure the normal functioning of the company's computer system.
Employees like to take advantage of the facilities in their companies to handle their personal matters.
Employees take anti-virus software, firewalls and IT staff as guarantees for the normal functioning of their PCs.
Employees welcome the free software available on the Internet and they download a lot of it.