An Israeli firm of private investigators has been rapped for using spyware to steal sensitive information.

According to reports, four members of the Israeli Modi'in Ezrahi private investigation company have been sentenced after being found guilty of using a Trojan horse to steal commercial information.

The Trojan, which was designed and marketed by London-based couple Michael and Ruth Haephrati, was said to have been used by a number of different private investigation firms to spy on companies including the HOT cable television group and Rani Rahav PR agency.

Another alleged victim was Champion Motors, which imports Audi and Volkswagen vehicles.

Asaf Zlotovsky, a manager at the Modi'in Ezrahi detective firm, was given a 19-month jail sentence. Two other employees, Haim Zissman and Ron Barhoum, were sent to prison for 18 and nine months respectively.

Yitzhak Rett, the firm's former chief executive, escaped a jail sentence after admitting the allegations under a plea bargain. He has been fined 250,000 Israeli Shekels (£36,500) and will face 10 months on parole.

"It is understandable that firms would want information on what their business rivals are planning to do, and try to seek a competitive advantage over them," said Graham Cluley, senior technology consultant at Sophos.

"What is not acceptable is to hire firms that will use illegal methods, such as computer spyware, to gather that information.

"Firms need to be very careful about the third parties they hire to help them grow their business, and seek assurances that their partners will not be behaving unethically or illegally.

"If they do not, the consequences could not only be a swathe of bad publicity but a spell in prison."