"Evidence shows that infiltration efforts target the monitoring of the Journal's coverage of China and are not an attempt to gain commercial advantage or to misappropriate customer information," Paula Keve, a spokeswoman for Journal publisher Dow Jones, said in a written statement.
She said data security is an "ongoing issue," and that the paper, part of Rupert Murdoch's News Corporation, continue "to work closely with the authorities and outside security specialists, taking extensive measures to protect our customers, employees, journalists and sources".
The Journal in recent weeks has been taking steps to overhaul network security. The effort was completed on Thursday, the daily said.
The New York Times had yesterday accused Chinese hackers of carrying out sustained attacks on its computer systems, breaking in and stealing the passwords of reporters, including in India, after the paper's expose of vast wealth amassed by Chinese Premier Wen Jiabao's family.
The WSJ in a report said the Journal has faced hacking threats from China during the past few years.
In the most recent incident, the Journal was notified by the FBI of a potential breach in the middle of last year, when the FBI came across data that apparently had come from the computer network in the Journal's Beijing bureau, people familiar with the incident said.
The Journal hired consultants to investigate the matter and uncovered a major breach in which hacking groups
