Jefferson County, Missouri, could not process transactions after officials took its network and phone systems offline in response to a security threat they are investigating as a possible cyberattack.
In a Friday alert, the county said problems with its phones and servers left it “temporarily unable to process any transactions.”
Administrators identified the threat on the county network Friday and shut down the network and phone systems as a precaution, First Alert 4 reported Tuesday. Officials were still determining its impact, the station said.
The disruption also affected county business. Jefferson County canceled its Board of Zoning Adjustment and Planning and Zoning Commission meetings scheduled for Thursday, according to Leader Publications.
Jefferson County lies south of St. Louis, has its seat in Hillsboro and had an estimated 233,000 residents in 2025.
Officials told First Alert 4 they had no indication of a data breach. They said the threat had not affected law enforcement operations at the Jefferson County Sheriff’s Office.
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“Our IT staff is working diligently to resolve the issue and restore normal service as quickly as possible,” the county said in its alert.
Terrebonne Parish Government in Louisiana also took systems offline last week, after officials reported a cyberattack. Residents could still obtain services in person, but the parish website was unavailable Wednesday evening.
Jefferson County has not described the threat, said whether anyone gained unauthorized access or announced when affected services will be restored.
