Adversaries may exfiltrate data to a cloud storage service rather than over their primary command and control channel. Cloud storage services allow for the storage, edit, and retrieval of data from a remote cloud storage server over the Internet.
Examples of cloud storage services include Dropbox and Google Docs. Exfiltration to these cloud storage services can provide a significant amount of cover to the adversary if hosts within the network are already communicating with the service.
Detection Strategy for Exfiltration to Cloud Storage
Restrict Web-Based Content: Restricting web-based content involves enforcing policies and technologies that limit access to potentially malicious websites, unsafe downloads, and unauthorized browser behaviors. This can include URL filtering, download restrictions, script blocking, and extension control to protect against exploitation, phishing, and malware delivery. This mitigation can be implemented through the following measures:
Deploy Web Proxy Filtering:
Enable DNS-Based Filtering:
Enforce Content Security Policies (CSP):
Control Browser Features:
Monitor and Alert on Web-Based Threats: