Unknown criminals attacked the city of Dunwoody’s computer systems on Christmas Eve, forcing a shutdown of all department networks for several days. The city’s police department and FBI are investigating.

No data was compromised during the cyber attack, according to the city.

The unknown criminals penetrated the city’s computer systems with “ransomware,” according to the city. Police Chief Grogan declined to give details on Dunwoody ransomware attack or what it did to the city’s networks.

In 2018, the city of Atlanta’s computer systems were attacked and various files were encrypted with the criminals demanding a ransom in exchange for the key to unlock them in what is known as ransomware.

The Dunwoody cyber attackers also demanded a ransom to be paid in bitcoin, a digital currency, Grogan said. He declined to give the amount demanded or more information on the ransom demands other than to say the city did not communicate with the attackers or pay the ransom.

“This is obviously under investigation … and we are working with the FBI to track down the bad guys,” Grogan said.

The city’s contracted IT company, InterDev, recognized a threat to the city’s computer systems on Christmas Eve and moved to shut down servers and disconnect computers to limit the attack’s impact, Grogan said.

“Once the issue was identified remotely … they shut down everything,” he said. “They did a really good job of recognizing the threat early and shutting down everything.”

Ashley Smith, InterDev’s director of government services, said in a news release that as soon a problem was detected, “we took immediate steps to protect the city’s infrastructure.”

Public safety was not compromised during the cyber attack, Grogan said. With the police department’s computers shut down, officers filled out paper reports, for example.

“We did things the old-fashioned way,” he said.

Data back-ups from an offsite server were used to fully restore systems, he said.

“No information was captured … and no information was comprised in the city’s system,” Grogan said.

Dunwoody has experienced small cyber attacks before. On Thanksgiving Day in 2016, hackers believed to be from the county of Turkey altered the city’s website to display a photo of the Turkish president and flag. The website was restored after about two days.

The Atlanta ransomware attack in 2018 shut down systems for paying water bills and handling city court cases and rendered useless the computer files of some City Council members, among other impacts.

Two Iranian men have been indicted on federal charges for allegedly committing the devastating cyber attack on city of Atlanta computers, as well as similar “ransomware” crimes around the U.S. and Canada.

Dyana Bagby is a staff writer for Rough Draft Atlanta, Reporter Newspapers, and Atlanta Intown.