The FBI's Pittsburgh field office, which runs many cyber security investigations, is trying to identify the people behind breaches of the Democratic National Committee's computer systems, the officials said. Those breaches, in 2015 and the first half of 2016, exposed the internal communications of party officials as the Democratic nominating convention got underway and helped undermine support for Hillary Clinton.
The Pittsburgh case has progressed furthest, but Justice Department officials in Washington believe there is not enough clear evidence yet for an indictment, two of the sources said.
Meanwhile the bureau's San Francisco office is trying to identify the people who called themselves ”Guccifer 2" and posted emails stolen from Clinton campaign manager John Podesta's account, the sources said. Those emails contained details about fundraising by the Clinton Foundation and other topics.
Beyond the two FBI field offices, FBI counterintelligence agents based in Washington are pursuing leads from informants and foreign communications intercepts, two of the people said.
This counterintelligence inquiry includes but is not limited to examination of financial transactions by Russian individuals and companies who are believed to have links to Trump associates. The transactions under scrutiny involve investments by Russians in overseas entities that appear to have been undertaken through middlemen and front companies, two people briefed on the probe said.
