Yamato Transport Co. said Thursday that security breaches have compromised the personal information of members of its online service, such as their names, addresses and credit card information.

About 30,000 unauthorized login attempts in total were made on its Kuroneko Members online membership service between Monday and Wednesday, said the unit of Yamato Holdings Co.

Of these, 3,467 were successful, allowing third parties to actually log in. Information of the breached accounts is likely to have been viewed by the parties.

The Kuroneko Members service allows registered users to apply online for re-delivery of missed parcels. About 28 million users are registered.

Login information leaked from online services of other companies may have been used in the unauthorized login attempts, Yamato Transport officials said.

There has been no report that any of the compromised information was misused, the officials said.

Holders of the breached accounts are required to change their passwords before logging in. The company is asking Kuroneko Members users to not use the same password used on other online services.

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