How to: avoid viruses, Trojans, worms and spyware

Use anti-virus software:

Install anti-virus software on all your desktops and servers, and ensure they are kept up to date. New viruses can spread extremely quickly, so have an updating infrastructure in place that can update all the computers in your company seamlessly, frequently, and at short notice. Run email filtering software at your email gateway as well, in order to protect your business from the threats of email-borne viruses, spam and spyware.
And don’t forget to protect your laptop computers and desktop computers used by home workers. Viruses, worms and spyware can easily use these devices to enter your business.

Block file types that often carry viruses:

These include EXE, COM, PIF, SCR, VBS, SHS, CHM and BAT fi le types. It is unlikely that your organization will ever need to receive fi les of these types from the outside world.

Block files with more than one fi le-type extension:

Some viruses disguise the fact that they are programs by using a double extension, such as .TXT.VBS, after their fi lename. At fi rst glance a fi le like LOVE-LETTER-FORYOU. TXT.VBS or ANNAKOURNIKOVA.JPG.VBS looks like a harmless text fi le or a graphic. Block any file with double extensions at the email gateway.

Ensure all programs are checked by the IT department:

Ensure that all programs received from the outside world via email go directly to your IT department or, in the case of small businesses, your IT person, for checking and approval. They can confi rm that it is virus-free, properly licensed, unlikely to conflict with existing software, and is suitable.

Subscribe to an email alert service:

An alert service can warn you about new viruses and offer virus identities that will enable your anti-virus software to detect them. Sophos has a free alert service. For details, see www.sophos.com/security/notifi cations. Consider adding a live virus information feed to your website or intranet to ensure your users know about the very latest computer viruses.

Use a fi rewall on computers connected to the internet:

You should use a fi rewall to protect computers that are connected to the outside world. Laptops and home workers will also need fi rewall protection.

Stay up to date with software patches:

Watch out for security news and download patches. Such patches often close loopholes that can make you vulnerable to viruses or internet worms. IT managers should subscribe to software vendors’ mailing lists such as that at www.microsoft.com/technet/security/bulletin/notify.mspx. Home users who have Windows computers can visit windowsupdate.microsoft.com, where you can scan your PC for security loopholes and find out which patches to install.

Back up your data regularly:

Make regular backups of important work and data, and check that the backups were successful. You should also fi nd a safe place to store your backups, perhaps even offsite in case of fi re. If you are infected with a virus, you will be able to restore any lost programs and data.

Disable booting from floppy disks:

Boot sector viruses are rarely seen now, but you may want to protect yourself from them. Change the bootup sequence on PCs so that they always boot from the hard disk fi rst, rather than trying to boot from fl oppy disk (drive A:). Then, even if an infected fl oppy disk is left in the computer, it cannot be infected by a boot sector virus. Should you need to boot from a fl oppy disk, the setting can easily be switched back.

Introduce an anti-virus policy:

Produce a policy for safe computing in the workplace and distribute it to all staff. Such a policy could include:
• Don’t download executables and documents directly from the internet.
• Don’t open unsolicited programs, documents or spreadsheets.
• Don’t play computer games or use screensavers which did not come with the operating system.
• Submit email attachments to the IT department for checking.
• Save all Word documents as RTF (Rich Text Format) fi les, since DOC fi les can harbor macro viruses.
• Treat any unexpected email with suspicion.
• Forward virus warnings or hoaxes directly to IT (and no-one else) to confi rm whether they are genuine or not.
• Inform IT immediately if you think your computer may have been infected with a virus.

Sophos.com