The hijacking of online brokerage accounts has suddenly become a problem in Japan, as the deep-pocketed and unsuspecting are targeted and their portfolios commandeered to manipulate the market.

For January and February, the Financial Services Agency reported 72 unauthorized online brokerage transactions. In March and April, that number was 3,400.

The Japan Securities Dealers Association said on Wednesday that it had confirmed hijacking cases at 16 brokerages, including major companies like SBI Securities and Rakuten Securities, and warned that alleged cyber crooks are now targeting users of smaller securities companies.