A ransomware attack darkened the video surveillance system of the District of Columbia’s police department eight days before the presidential inauguration of Donald J. Trump. Video storage devices for 70 percent of the CCTV system reportedly were unable to record anything between Jan. 12 and Jan. 15, as police techies scrambled to combat malicious software found on 123 of 187 networked video recorders. However, the safety of the public was never in jeopardy during the camera blackout, a Secret Service official said.