Adversaries may alter data en route to storage or other systems in order to manipulate external outcomes or hide activity, thus threatening the integrity of the data.(Citation: FireEye APT38 Oct 2018)(Citation: DOJ Lazarus Sony 2018) By manipulating transmitted data, adversaries may attempt to affect a business process, organizational understanding, and decision making. Manipulation may be possible over a network connection or between system processes where there is an opportunity deploy a tool that will intercept and change information. The type of modification and the impact it will have depends on the target transmission mechanism as well as the goals and objectives of the adversary. For complex systems, an adversary would likely need special expertise and possibly access to specialized software related to the system that would typically be gained through a prolonged information gathering campaign in order to have the desired impact.
Monitor for anomalies in transmitted data streams, including mismatched file integrity checks, API interception, or man-in-the-middle modifications. Detect unexpected use of APIs that handle network I/O where transmitted data integrity could be manipulated.
Detect alterations of transmitted data via monitoring syscalls (`send`, `recv`, `write`) or middleware interception. Identify mismatched file hashes when compared at origin vs. destination. Watch for anomalous activity from processes interacting with secure transmission services (e.g., OpenSSL, scp).
Monitor system APIs such as CFNetwork and SecureTransport for anomalies in transmitted data streams. Detect mismatches in file hashes or SSL/TLS downgrade attempts that enable manipulation of transmitted data.