The Honolulu Police Department confirmed that its old public alert system was hacked by “an unauthorized person or persons” over the weekend, compromising information not just of the department but the email addresses, cellular phone numbers and passwords of 3,500 people who signed up for HPD email or text message alerts.

HPD spokeswoman Michelle Yu, in an email said: “Subscribers’ names, phone numbers and email addresses were compromised.”

The department has since removed the data base and added new measures to protect the information, the email said. “At no time did the breach affect police services,” she said.

“HPD Alerts was a pilot program (used) to provide breaking information to the public,” Yu said. “It was recently discontinued due to technical problems not associated with the cyberattack.”

HPD about two months ago went back to widely used Nixle system to inform the public of road closures, tsunami warnings or other information affecting large numbers of Oahu residents.

Late Monday afternoon, HPD sent an email to the subscribers urging them to "monitor your online activity and Internet accounts. If you use the same password for other accounts, please consider changing passwords."

Several web sites devoted to Internet security information – namely pastebin.com and hackread.com – said the attack was initiated by a hacker known as “X-Blackerz Inc” who apparently did it as as part of #OpUSA, an action conducted in protest of the U.S. government’s military actions in the Middle East.

OpUSA is supposed to hit government agencies and private businesses en masse tomorrow although it is not expected to cause widespread disruption, according to an article in the Huffington Post.