Story highlights The Justice Department has prepared an indictment against people thought to be behind the attack, according to the officials

An announcement could come in the next week, sources say

Washington (CNN) The Obama administration is preparing to publicly attribute a 2013 cyber attack against a New York dam to Iranian hackers, according to U.S. officials familiar with the investigation.

The Justice Department has prepared an indictment against people thought to be behind the attack, according to the officials. An announcement could come in the next week.

The intrusion at the Bowman Avenue Dam, around 30 miles north of New York City in suburban Rye Brook, New York, isn't considered sophisticated -- the hackers managed only to get access to some back office systems, not the operational systems of the dam, U.S. officials say. U.S. investigators quickly determined the attack was carried out by hackers working for the Iranian government.

But the attack alarmed Obama administration officials who have voiced concerns about the vulnerability of U.S. infrastructure to cyber attacks.

White House and Justice Department spokesmen declined to comment on plans to attribute blame for the attack. But Justice Department spokesman Marc Raimondi said in a statement that the agency takes "malicious activity in cyberspace seriously, and we will continue to use all the tools at our disposal to prevent, deter, detect, counter and mitigate such activity."

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