A employer analyzes malicious codes after massive hacking attack on TV broadcasters and banks at a monitoring room in Seoul, South Korea, March 21, 2013. (Xinhua/Park Jin-hee)

BRUSSELS, May 22 (Xinhua) -- Cyber criminals have devised ways of infecting the computers of thousands of Belgian companies, De Tijd reported on Friday.

Around 35,000 companies and professionals that use online banking via the Isabel system are potential targets.

Prosecutors in Brussels and Veurne have already opened investigations into the hacking threat after some Isabel customers reported the loss of considerable sums of money.

Bart Van Opstal of the Royal Federation of Belgian Notaries told De Tijd that "a large sum of money" has been stolen by computer hackers through the Isabel system.

Isabel also confirmed that the number of computer hacking attempts has "increased in recent months."