The top five internal security threats

Research conducted by the US Computer Emergency Response Team (Cert) estimates that almost 40 percent of IT security breaches are perpetrated by people inside the company.

Criminal attacks are particularly likely to happen from the inside: one recent study estimated that 90 percent of criminal computer crimes were committed by employees of the company attacked.

Smaller businesses are uniquely vulnerable to IT security breaches because they may lack the more sophisticated intrusion detection and monitoring systems used by large enterprises, according to Mark Murtagh, a technical director with Websense. "We definitely are seeing an increasing threat to SMEs, coupled with a lack of understanding of the threats posed," he says.