Activity from Amazon's real-time digital advertising auction may be responsible for much of the traffic overwhelming the firewall, according to internal Slack messages seen by Insider.

Even inside AWS, however, information on the outage remains sketchy. One AWS employee speculated that the outage was caused by an "orchestrated DNS attack," while another employee downplayed those concerns, saying it was more of an "internal thing" related to networking and firewall saturation.

"It's the fog of war," said an AWS manager.