The University of Maryland Medical System says an external attempt was made on Sunday to infiltrate their IT network at multiple campuses.
After learning of the threat, UMMS as a precaution downed much of its IT system.
During the disruption, affected hospitals implemented backup operational procedures, to ensure continuity of patient care.
A UMMS spokesman provided a statement to WMAR-2 that said in part:
"Our robust threat monitoring system worked as designed, and we worked quickly to identify, isolate and remedy the issue to ensure the threat was mitigated before bringing systems back online."
The spokesman added some "non-emergent functions may have seen minimal impacts at some local hospital campuses."