According to NBC News, hackers—allegedly from Russia— compromised an unclassified email system used by more than 4,000 employees of the Joint Chiefs of Staff. The attack apparently began on or about July 25 and was “coordinated … via social media accounts.”
CBS News reports that classified elements of the network were not affected. Nevertheless, the unclassified servers remain offline, “and senior members of the Joint Staff were provided with an alternative means of exchanging unclassified e-mail.”
While NBC News suggests that Russia is the primary suspect, the actual source of the attack is not yet absolutely clear. CNBC says “a state actor” is responsible, but it does not say whether the attack “was sanctioned by the Russian government or conducted by individuals.” The “attribution problem”—the difficulty of determining who is responsible for an attack—is increasingly part of cybersecurity discussions.