Although most Americans do not consider the FBI to be an intelligence agency, they are, in fact, one of the famous 3 - letter agencies (CIA, NSA, DIA, NRO, etc) and they are responsible for seeing that bad people who are attacking American citizens or corporations or whatever are thwarted. Particularly when whatever is happening takes place inside our national borders where agencies like the CIA are not allowed to operate, generally speaking.
Of course, certain announcements by the FBI regarding Cyberwar have not always worked out. For example, SONY was probably not hacked by North Korea, but rather by a very spiteful and talented former employee and IT worker.
Nevertheless, it is the FBI's job in all this to investigate but also to educate and warn Americans who may be at risk. Hence this alert.