Democratic National Committee cyber attacks

The Democratic National Committee cyber attacks took place in 2015 and 2016, in which computer hackers infiltrated the Democratic National Committee (DNC) computer network, leading to a data breach. Some cybersecurity experts, as well as the U.S. government, stated that the cyberespionage was the work of Russian intelligence agencies.

Forensic evidence analyzed by several cybersecurity firms, CrowdStrike, Fidelis, and Mandiant (or FireEye), strongly indicates that two Russian intelligence agencies infiltrated the DNC computer systems. The American cybersecurity firm CrowdStrike, which removed the hacking programs, revealed a history of encounters with both groups and had already named them, calling one of them Cozy Bear and the other Fancy Bear, names which are used in the media.

Cyber attacks that successfully penetrated the DNC computing system began in 2015. Attacks by "Cozy Bear" began in the summer of 2015. Attacks by "Fancy Bear" began in April 2016. It was after the "Fancy Bear" group began their activities that the compromised system became apparent. The groups were presumed to have been spying on communications, stealing opposition research on Donald Trump, as well as reading all email and chats. Both were finally identified by CrowdStrike in May 2016. Both groups of intruders were successfully expelled from the DNC systems within hours after detection. These attacks are considered to be part of a group of recent attacks targeting U.S. government departments and several political organizations, including 2016 campaign organizations.

...
Wikipedia