“The expulsion of 35 Russian diplomats, the shutting down of two Russian-owned estates the US claims were used for intelligence activities, and the targeted financial sanctions on Russian individuals and organizations all show the Obama administration understands at least part of what such a firm response should entail.
Unfortunately, the White House was unable to produce the most critical part for the credibility of their action: that to be politically effective in today’s Internet age, such a response also needs to be backed up with solid evidence. Here, the administration failed miserably, but also predictably. And it’s not necessarily because it doesn’t have the evidence. Instead, the U.S. government simply failed to present it.”
Source: The DHS/FBI Report on Russian Hacking was a Predictable Failure | Just Security