Ryan K. Dickey was assigned to Mueller’s team in early November from the Justice Department’s computer crime and intellectual-property section.

Dickey’s addition is particularly notable because he is the first publicly known member of the team specializing solely in cyber issues. The others’ expertise is mainly in a variety of white-collar crimes, including fraud, money laundering and public corruption.

Mueller's team has charged or negotiated plea deals with four former Trump campaign or administration officials, including former national security adviser Michael Flynn and former campaign manager Paul Manafort.