In June 2016, it will be reported that the computer network of the DNC [Democratic National Committee] was compromised for about a year. Around May 2016, the security company CrowdStrike is hired by the DNC to investigate and stop the hacking attack. According to CrowdStrike, there actually are two different groups that successfully break into the network, both of them linked to the Russian government.
The first group is said to be known by the nickname Cozy Bear. In 2015, it allegedly successfully infiltrated the unclassified networks of the White House, State Department, US Joint Chiefs of Staff, and others. This group gets into the DNC’s network in the summer of 2015 and is not stopped until May 2016.
The second group is said to be known by the nickname Fancy Bear, and it also has had many other successful attacks. It gets into the network in April 2016 and also is stopped in May 2016.
On June 15, 2016, someone going by the nickname “Guccifer 2.0” posts DNC files on the Internet. This person claims to have no connection to the Russian government, but also claims to have accessed the DNC network for “almost a year,” which is similar to what CrowdStrike says about Cozy Bear. (CrowdStrike.com, 6/15/2016) (The Washington Post, 6/15/2016)