Corporate bank accounts were increasingly targeted by swindlers in the first half of the year, and online thefts have already surpassed last year's record total, according to National Police Agency data released Thursday.

Roughly ¥1.852 billion was taken from the accounts of unsuspecting clients between January and June, surpassing the full-year record of around ¥1.406 billion logged in 2013, the NPA said.

The attacks have hit 73 banks so far, but corporate accounts at regionals are being heavily targeted as the online robberies proceed unchecked. An agency spokesman said it appears many of the victims were small and midsize companies.

"Compared with big businesses, many of these companies may have lax security measures," the NPA official said.

Around ¥572 million was fraudulently withdrawn from corporate accounts in the first half, representing an almost sixfold increase from last year. By institution, regional banks logged a more than fourfold increase in stolen money, bringing the total to around ¥519 million.

Corporate accounts at regional lenders saw around ¥410 million in funds stolen, up nearly ninefold.

Half-year fraud cases totaled 1,254 overall, resulting in around ¥1.48 million in damage per case.

A total of 73 banks were hit by online fraud, including big names such as Mizuho Bank, Sumitomo Mitsui Banking Corp. and Bank of Tokyo-Mitsubishi UFJ. The majority, or 59, were regional institutions such as Bank of Fukuoka, Gunma Bank and Hokkaido Bank.

One of the most common ways being used to access the accounts is computer viruses to steal IDs and passwords, but criminals are also developing programs specifically geared to the websites of individual banks, the agency said.

The NPA advises using a dedicated PC for online banking that is separate from those used to contact others online, because viruses are often embedded in email.