An early clue that something was amiss with the computers at New York City’s Law Department — the 1,000-lawyer agency that represents the city in court — emerged on Monday when a lawyer for the department wrote to a federal judge in Manhattan, asking for a short delay in filing court papers because of “connectivity” problems.
“No one is currently able to log on to the Law Department’s computer system,” the lawyer, Katherine J. Weall, wrote.
Later in the day, city officials revealed the cause of the problem: They had been forced to disable the Law Department’s computer network on Sunday afternoon after detecting a cyberattack. That attack is now under investigation by the intelligence bureau of the New York Police Department and the F.B.I.’s cyber task force, the officials said.
Mayor Bill de Blasio said during a NY1 television appearance on Monday evening that city officials were not aware of any information being compromised or a ransom demand. But he cautioned that the situation was “emerging.”
“We’ll have more to say as we get more information,” he said. “So far we believe the defenses have held and the Law Department’s information was not compromised.”
The hack was first reported by The Daily News.
It remained unclear on Monday who was behind it or what the hackers’ goal was, according to a city official briefed on the incident. The official said that the type of ransomware used is commonly deployed by criminal groups and hackers associated with foreign governments. .
City officials said they had disconnected the Law Department computers from the city’s larger network on Sunday afternoon.
The attack comes as the United States government and businesses have raised alarm about recent ransomware attacks on such targets as a critical gas pipeline, the world’s largest meat processor and the police department in Washington, D.C. The White House warned American businesses last week to take urgent security steps to guard against ransomware attacks, and in a published interview, Christopher A. Wray, the F.B.I. director, likened the ransomware threat to that posed by global terrorism after the Sept. 11, 2001, attacks.
Hackers use ransomware to break into government and private computer networks. Once inside, they can lock out the owners or steal data that is used to demand a ransom. The frequency of attacks has risen over the last several years.
Concerns about a possible attack first arose on Saturday evening, when the city’s Cyber Command detected unusual activity on the Law Department’s computer network, according to the official briefed on the incident. The command is a unit Mr. de Blasio created by executive order in 2017 to defend the city’s computer systems.
Nicholas Paolucci, a Law Department spokesman, said the agency was taking steps “to ensure there was minimal impact to cases” and to keep the department’s functions moving forward.
The effect on other city agencies remained unclear on Monday. “Until we understand the full breadth of breach we’re trying to move cautiously,” said Lucian Chalfen, a spokesman for the state court system, where the Law Department represents the city in lawsuits.