Exploitation of DNS Tunneling for Optimization of Data Exfiltration in Malware-free APT Intrusions

Abstract

One of the main goals of targeted attacks include data exfiltration. Attackers penetrate systems using various forms of attack vectors but the hurdle comes in exfiltrating the data. APT attackers even reside in a host for long periods of time whilst seeking the best option to exfiltrate data. Most data exfiltration techniques are prone to detection by intrusion detection system. Therefore, data exfiltration methodologies that generate little noise if any at all are attractive to attackers and can go undetected for long periods owing the low threshold of generated noise in form network traffic and system calls. In this paper, we present malware-free intrusion, an attack methodology which does not explicitly use malware to exfiltrate data. Our attack structure exploits the use of system services and resources not limited to RDP, PowerShell, Windows accessibility backdoor and DNS tunneling. Results show that it’s possible to exfiltrate data from vulnerable hosts using malwarefree intrusion as an infection vector and DNS tunneling as a data exfiltration technique. We test the attack on both Windows and Linux system over different networks. Mitigation techniques are suggested based on traffic analysis captured from the established secure DNS tunnels on the network.