For the past two weeks, the unclassified email system serving the Joint Chiefs of Staff has been down — and a report today from NBC News suggests there may be more to the outage than meets the eye. NBC says the downtime is the result of a "sophisticated cyberattack" from Russian attackers, citing US officials. Officials said it's still unclear whether the attack is linked to the government or individuals residing in Russia. The email system is expected to come back online this week.

The result is alarming, although not as damaging as recent intrusions into the State Department or the Office of Personnel Management. It's also unclear how the officials named in the piece linked the attack to Russia, given the historical difficulty of making an affirmative attribution. It doesn't appear any classified information was compromised by the breach, but given the military importance of the joint chiefs, the outage is still cause for concern.