BALTIMORE — The hack that forced Baltimore ’ s 911 dispatch system to be temporarily shut down over the weekend was a ransomware attack, Attack.Ransom city officials said Wednesday . Such a ttacks Attack.Ransom — another of which occurred in Atlanta last week — take over parts of private or municipal computer networks and then d emand payment, Attack.Ransom or r ansom, Attack.Ransom for their release . Frank Johnson , chief information officer in the Mayor ’ s Office of Information Technology , said he was not aware of any specific r ansom request Attack.Ransom made by the hackers of Baltimore ’ s network , but federal authorities are investigating . “ The systems and the software and the files are all being investigated by the FBI right now , ” Johnson said . No personal data of city residents w as compromised, Attack.Databreach he added . Dave Fitz , an FBI spokesman , could not be reached Wednesday . On Tuesday , Fitz said the agency was aware of the breach and providing assistance to the city , but otherwise declined to comment . The attack infiltrated a server that runs the city ’ s computer-aided dispatch , or CAD , system for 911 and 311 calls . The system automatically populates 911 callers ’ locations on maps and dispatches the closest emergency responders there more seamlessly than is possible with manual dispatching . It also relays information to first responders in some cases and logs information for data retention and records . The breach shut down the CAD system from Sunday morning until Monday morning , forcing the city to revert to manual dispatching during that time . While the city ’ s 911 calls are normally recorded online on Open Baltimore , the city dispatch logs stopped recording them at 9:54 a.m. Sunday and didn ’ t resume recording them again until 7:42 a.m. Monday . Johnson said the attack was made possible after a city information technology team troubleshooting a separate communications issue with the server inadvertently changed a firewall and left a port , or a channel to the Internet , open for about 24 hours , and hackers who were likely running automated scans of networks looking for such vulnerabilities f ound Vulnerability-related.DiscoverVulnerability it and gained access . The Baltimore hack comes amid increasing hacking of municipal systems across the country , and follows one in Atlanta last week that paralyzed that city ’ s online bill-payment system , with hackers d emanding Attack.Ransom a $ 51,000 p ayment Attack.Ransom in bitcoin to unlock it . T hat attack Attack.Ransom occurred Thursday , and Atlanta employees only turned their computers back on Tuesday . Johnson said his office works diligently to prevent cyberattacks and is looking to invest more in safeguarding its networks . Baltimore also faced cyberattacks during the unrest in 2015 , when its website was taken offline . Johnson said he was unaware of any other successful attacks on the city ’ s networks . He said the city would be obligated to disclose any a ttacks Attack.Databreach that c ompromised Attack.Databreach residents ’ personal information , health information or crime data . Johnson said he feels the city recovered well from the breach once it was identified , but that he did not want to go into detail about what was done lest he expose the city to more attacks . The city has a $ 2.5 million contract with TriTech Software Systems to maintain its CAD software and provide “ technical support services to ensure the functional integrity ” of the city ’ s CAD system . Scott MacDonald , TriTech ’ s vice president of public safety strategy , said the company worked with city IT personnel to shut down the CAD software after the attack . The breach was not related to the company ’ s software , MacDonald said . “ Our techs connected and worked with the IT staff there , and the CAD system was taken down manually , in combination between our staff and theirs , while the servers could be troubleshooted by the city . ”