With upwards of 40,000 computer viruses lurking out there, you need to coach your team to play strong defense. Take these steps: Buy new anti-virus software. Arrange to run automatic updates of it monthly. Warn everyone not to open unsolicited e-mail attachments and never to click on “funny” online video clips—you never know the source and whether they’re infested with bugs. Finally, don’t set your Web browser to download and open Internet files automatically. Instead, check every incoming message for viruses before you open it.