On March 14, 2013, the Romanian hacker known as Guccifer broke into the email account of Clinton confidant Sid Blumenthal and learned Clinton’s private email address and thus her clintonemail.com server domain.
A September 2016 FBI report will reveal that “An examination of log files [of Clinton’s server] from March 2013 indicated that IP addresses from Russia and Ukraine attempted to scan the server on March 15, 2013, the day after the Blumenthal compromise, and on March 19 and March 21, 2013. However, none of these attempts were successful, and it could not be determined whether this activity was attributable to [Guccifer].” (Federal Bureau of Investigation, 9/2/2016)