The enemy within the firewall
I've been telling this to people for years, the biggest threat to a network comes from within a company. Even if you have a layered security system, this will not protect you against people who wants to steal confidential data from inside your network, unless you planned your architecture with internal security in mind.
The Age is reporting that many businesses are now considering employees a much bigger threat to security than most external threats. It appears that some criminal gangs have started to recruit employees to steal insider knowledge instead of having someone bust through the firewall to steal that sensitive data.
"With email and instant messaging proving increasingly popular and devices such as laptop computers, mobile phones and USB storage devices more commonplace in the office, the opportunities for workplace crime are growing."