The secretary of state of Georgia is asking the Department of Homeland Security to explain what appears to be an attempted breach of the state’s computer systems that house its voter registration database by someone in the federal government.

In a letter to Department of Homeland Security Secretary Jeh Johnson dated Thursday, Georgia’s Secretary of State Brian Kemp said the state had discovered an unsuccessful attempt to breach the firewall of state computer systems. The attempt occurred on Nov. 15 and was linked to an IP...