WASHINGTON -- considering the serious warnings lately about Internet viruses (病毒), users may don’t use their machines just to keep them safe. In reality, common sense and a few basic tips can keep Internet surfers secure. Anti-vires software is a must, and it should be updated at least once a week to recognize newly viruses. If this is not done, you will meet great troubles. People with broadband Internet connections should have also a firewall, These protect the computer from attacks by hackers (黑客). Then it is time to think about computer habits. Unlike old viruses, which spread only through shared disks, the Internet brings viruses straight to the e-mail box. If an e-mail with attachment (附件) comes from an unknown sender, or unexpectedly from a known sender, it should not be opened. On receiving an unexpected attachment from a friend, experts suggest a telephone call to make sure of the mail’s source before opening. If you open the mail without any consideration, you will be easily attacked by the hackers. Which of the following is NOT right according to the passage
A．Something can be done to keep our computers safe. B．Even an e-mail attachment coming from a friend may not be safe to open. C．We should not use our computers to defend ourselves from viruses. D．Anti-virus software made some years ago is hard to protect today’s computers.