Two thirds of firms are without full insurance for business crime, which costs companies an average of £5,000 a year, according to a survey from the Institute of Directors (IOD).
The IOD's research showed that a quarter of UK executives reported that their businesses had suffered a crime within the past 12 months.
It also found that only a third of businesses have fully comprehensive insurance to cover such crimes, with most victims forced to increase security repair damage, pay higher premiums and cope with disruption to trading.
The biggest business crime is theft by non-employees, which comprises two thirds of all offences.
The IOD's survey also revealed high levels of fraud and internet crime, which affected 30% and 37% of firms respectively.