There are two questions here:
Are there 17 US intelligence agencies?
From the home page of the Office of the Director of National Intelligence (ODNI) (emphasis mine):
The U.S. Intelligence Community is a coalition of 17 agencies and organizations, including the ODNI, within the Executive Branch that work both independently and collaboratively to gather and analyze the intelligence necessary to conduct foreign relations and national security activities.
Besides the ODNI, the other 16 are
- The U.S. Air Force Intelligence, Surveillance, and Reconnaissance (USAF ISR) Enterprise of the U.S. Air Force,
- The Office of Terrorism and Financial Intelligence of the Department of the Treasury,
- The U.S. Army Intelligence and Security Command,
- The Office of National Security Intelligence of the Drug Enforcement Administration,
- The Central Intelligence Agency,
- The Intelligence Branch of the Federal Bureau of Investigation,
- The Coast Guard Intelligence of the United States Coast Guard,
- The Intelligence Department of the United States Marine Corps,
- The Defense Intelligence Agency,
- The National Geospatial-Intelligence Agency,
- The Office of Intelligence and Counterintelligence in the Department of Energy,
- The National Reconnaissance Office,
- The Office of Intelligence and Analysis of the Department of Homeland Security,
- The National Security Agency,
- The Bureau of Intelligence and Research of the Department of State, and
- The Office of Naval Intelligence of the United States Navy.
Did these 17 intelligence agencies claim that Russia was behind the email leak?
Yes, kind of.
In an October 2016 Joint Statement from the Department Of Homeland Security and Office of the Director of National Intelligence on Election Security [Hat-tip: @tim] it was reported:
The U.S. Intelligence Community (USIC) is confident that the Russian Government directed the recent compromises of e-mails from US persons and institutions, including from US political organizations.
This does not imply each of the 17 agencies conducted a different, independent investigations. It means that they reached a consensus view and published together.
The JAR-1620296 Joint Analysis Report titled GRIZZLY STEPPE – Russian Malicious Cyber Activity was issued earlier this week.
This Joint Analysis Report (JAR) is the result of analytic efforts between the Department of Homeland Security (DHS) and the Federal Bureau of Investigation (FBI).
It expands on the joint statement, but is, admittedly, rather weak on substance:
In spring 2016, APT28 compromised the same political party, again via targeted spearphishing.
This time, the spearphishing email tricked recipients into changing their passwords through a fake webmail domain hosted on APT28 operational infrastructure. Using the harvested credentials, APT28 was able to gain access and steal content, likely leading to the exfiltration of
information from multiple senior party members. The U.S. Government assesses that information was leaked to the press and publicly disclosed.
The ODNI released a slightly more substantial report this afternoon entitled Assessing Russian Activities and Intentions in Recent US Elections, "a declassified version of a highly classified assessment that has been provided to the President and to recipients approved by the President." The background to this report (the first two pages of the linked file) writes about the "Intelligence Community" as a whole. The details show that just three of the sixteen agencies, plus the ODNI, were active in this investigation:
This report includes an analytic assessment drafted and coordinated among The Central Intelligence Agency (CIA), The Federal Bureau of Investigation (FBI), and The National Security Agency (NSA), which draws on intelligence information collected and disseminated by those three agencies.
That the remaining twelve organizations are not recognized (publicly) does not mean that those other twelve don't agree with the assessment. Cyber security is not the bailiwick of (for example) the National Reconnaissance Office, who build and operate spy satellites, or the National Geospatial-Intelligence Agency, who use data from those spy satellites and other sources to provide geographic intelligence.
Did those three agencies (plus the ODNI) claim that Russia was behind the email leak? Absolutely. Emphasis not mine:
We assess Russian President Vladimir Putin ordered an influence campaign in 2016 aimed at the US presidential election. Russia’s goals were to undermine public faith in the US democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency. We further assess Putin and the Russian Government developed a clear preference for President-elect Trump. We have high confidence in these judgments.
We also assess Putin and the Russian Government aspired to help President-elect Trump’s election chances when possible by discrediting Secretary Clinton and publicly contrasting her unfavorably to him. All three agencies agree with this judgment. CIA and FBI have high confidence in this judgment; NSA has moderate confidence.
Moscow’s approach evolved over the course of the campaign based on Russia’s understanding of the electoral prospects of the two main candidates. When it appeared to Moscow that Secretary Clinton was likely to win the election, the Russian influence campaign began to focus more on undermining her future presidency.
Further information has come to light since Election Day that, when combined with Russian behavior since early November 2016, increases our confidence in our assessments of Russian motivations and goals.
That said, cyber security authors outside of the U.S. Intelligence Community find both the JAR and the more recent release to be a bit lacking in substance. For example Feds’ Damning Report on Russian Election Hack Won’t Convince Skeptics. There are lots and lots of other similar blogs and reports.
However, those cyber security authors don't have access to the classified information behind those findings. The Republican Senators and Representatives who do have access to that information are quite resolute: It was Russians who did this. It was not China nor some hypothetical 14 year old (and many other sources).
Hopefully what comes out next week will be a bit more substantial.
I suspect that the report released earlier today is close to the last public word on this subject. Releasing the highly classified details would entail disclosing sensitive ways and means that just might weaken U.S. security in the future.