After gaining ‘blind’ command execution access to a compromised Linux host, data exfiltration can be difficult when the system ibinbash2s protected by a firewall. Sometimes these firewalls prevent the compromised host to establish connections to the internet. In these cases, data exfiltration through the DNS-protocol can be useful. In a lot of cases DNS-queries are not blocked by a firewall. I’ve had a real life situation like this, which i will describe later on.