Even more shocking is that upwards of 50 per cent are caused by the company 's own network administrators.
So what can you do to protect your network? Here 's a list of tips culled from industry analysts, security experts, corporate executives and agents of the US Secret Service:
Make sure no one person is controlling the system front to back.
Require every person logging on to use a password.
Assign supervisory rights to as few people as possible.
Back up mission-critical systems daily.
Back up all systems weekly.
Have a strict sign-in/sign-out system for backup tapes.
Always have a current copy of the backup tape stored remotely.
Do backups of desktops and laptops as well as servers.
Rotate backup tapes - don't keep using the same one over and over again.
Change passwords every three months.
Keep servers in a secured area.
Stay up to date on software patches.
Use intrusion-detection software that alerts you when you are being hit.
Make sure two pairs of eyes have checked code before it is entered into the system.
Have an information security department (at least one person and then one other for every 1000 users) that is separate from the IT department and reports directly to the chief information officer.
Spend at least 3 per cent to 5 per cent of the IS budget on information security.
Train information security personnel to be aware of any employee who shows signs of being troubled or disgruntled, particularly if that employee holds an information-critical position.
Beef up security during certain events, such as mergers or downsizings, that could upset workers and cause them to lash out at the company.
Monitor the network - set up software that will alert you if the person is working in a different part of the network or at a different time than usual.
Scan e-mail to see what's going out of the company, double-check backup tapes and have someone else do the backups if that person is the one in question.
Make sure the person in charge of the system is not the same person in charge of the backup.
Have specific policies and punishments built into employee contracts.
Make sure critical IS workers are bonded.
Know how to protect your system if you're firing a network administrator:
Change everyone's passwords so he/she can't use them to break into the system.
Verify that your backup tapes are where they should be; make sure the information has been saved correctly and the tape is functioning properly.
Do a new backup.
Lock down every system that person had access to on the day of termination.
Have a new network administrator ready to step into the open position immediately.
Go up on the system and check user names and passwords, looking for anything unusual.
Make sure every logon has a password for it.
Lock down all the inside doors, such as the file servers, application servers and mail servers.
Look for backdoors on the system, such as Back Orifice on Windows NT.
Make sure there aren't any known vulnerabilities that haven't been patched - the administrator could have left those holes behind so he could get back in.
Strengthen your intrusion-detection system.
Set a trip wire - software that alerts the administrator to system anomalies, such as the size of a file changing.