Since X-Agent was found being used in an operation with obvious Russian military application, which therefore must be GRU, then GRU must be the entity that also hacked the DNC, because it used a common tool.
CrowdStrike’s founder, Dmitri Alperovitch, told PBS that this amounted to DNA tying Russia to both the DNC hack and the Ukrainian artillery app.

Essentially the DNA of this malicious code that matches to the DNA that we saw at the DNC.

Link zur Quelle