T1048.002 Exfiltration Over Asymmetric Encrypted Non-C2 Protocol
Adversaries may steal data by exfiltrating it over an asymmetrically encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.
Asymmetric encryption algorithms are those that use different keys on each end of the channel. Also known as public-key cryptography, this requires pairs of cryptographic keys that can encrypt/decrypt data from the corresponding key. Each end of the communication channels requires a private key (only in the procession of that entity) and the public key of the other entity. The public keys of each entity are exchanged before encrypted communications begin.
Network protocols that use asymmetric encryption (such as HTTPS/TLS/SSL) often utilize symmetric encryption once keys are exchanged. Adversaries may opt to use these encrypted mechanisms that are baked into a protocol.
||APT28 has exfiltrated archives of collected data previously staged on a target’s OWA server via HTTPS.
||APT29 has exfiltrated collected data over a simple HTTPS request to a password-protected archive staged on a victim’s OWA servers.
||Data Loss Prevention
||Data loss prevention can detect and block sensitive data being uploaded via web browsers.
||Filter Network Traffic
||Enforce proxies and use dedicated servers for services such as DNS and only allow those systems to communicate over respective ports/protocols, instead of all systems within a network.
||Network Intrusion Prevention
||Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary command and control infrastructure and malware can be used to mitigate activity at the network level.
||Follow best practices for network firewall configurations to allow only necessary ports and traffic to enter and exit the network.