There wouldn't be any weird outbound traffic; the attacker would use another cloud instance as a controller. They would use a US-based account (and IPs via VPNs) to control the controller.
The chip passes the stolen data between the VM instances by DMA. The stolen data hitches a ride inside an otherwise innocuous TCP packet storing log entries in that S3 bucket.
Logs are routine backed up off site.
There would be absolute nothing at the network level to distinguish the infiltrated packets.
Lower latency scenarios could be devised which would be similarly invisible but allow better command & control.
Original article supposes that the implanted chip was used to modify the boot process of the BMC in such a way that the BMC loaded its software over the network. The question is why this network activity wasn't easily detectable and firewalled off by default.
It seems that you suppose that the chip can be directly used for some sort of userspace-inside-a-VM to ring0(?) escalation. In particular, you suppose that the chip has access to main memory. Can you elaborate on what functionality do you think the implant could've had?
Or if they can insert themselves into the maintenance team, they can retrieve their chips at a later date.
Or you can just use the default credentials Cisco is addicted to leaving in their code.
can you imagine how it would go down if a major corporation like apple experienced a hardware hacking based infrastructure breach, contracted a cybersecurity company, and the tech heading their case asked them like "well were you making sure to check which ports were open?"