T1567 - Exfiltration Over Web Service

Adversaries may use an existing, legitimate external Web service to exfiltrate data rather than their primary command and control channel. Popular Web services acting as an exfiltration mechanism may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to compromise. Firewall rules may also already exist to permit traffic to these services.

Web service providers also commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Atomic Tests:

Currently, no tests are available for this technique.

Detection

Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. User behavior monitoring may help to detect abnormal patterns of activity.

Shield Active Defense

Behavioral Analytics

Deploy tools that detect unusual system or user behavior.

Instrument a system to collect detailed information about process execution and user activity, develop a sense of normal or expected behaviors, and alert on abnormal or unexpected activity. This can be accomplished either onboard the target system or by shipping data to a centralized analysis and alerting system.

Opportunity

There is an opportunity to detect the presence of an adversary by identifying and alerting on anomalous behaviors.

Use Case

Defenders can detect adversaries attempting to exfiltrate over web services by implementing behavioral analytics. This can detect a system connecting to these web services that it might not normally connect to, or during a time when it normally doesn’t do so.

Procedures

Use behavioral analytics to detect Living Off The Land Binaries (LOLBins) being used to download and execute a file. Use behavioral analytics to identify a system running development tools, but is not used by someone who does development. Use behavioral analytics to identify abnormal system processes being used to launch a different process.