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.

Positive Technologies products that cover the technique

MaxPatrol SIEM knowledge base

— Monitoring of events related to execution of tapinstall.exe. — Monitoring of Windows events with ID 7045 where ImagePath contains 'tap0901'. — Monitoring of events related to execution of dnscat2.exe or the Start-Dnscat2 PowerShell cmdlet.

Expert Required. The technique is detected only with the combination of «PT Product + Expert»

Detection

ID	DS0029	Data source and component	Network Traffic: Network Traffic Flow	Description	Monitor network data for uncommon data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious.

ID	DS0029	Data source and component	Network Traffic: Network Traffic Content	Description	Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).

ID	DS0017	Data source and component	Command: Command Execution	Description	Monitor executed commands and arguments that may steal data by exfiltrating it over a symmetrically encrypted network protocol other than that of the existing command and control channel.

ID	DS0022	Data source and component	File: File Access	Description	Monitor files viewed in isolation that may steal data by exfiltrating it over a symmetrically encrypted network protocol other than that of the existing command and control channel.

ID	DS0029	Data source and component	Network Traffic: Network Connection Creation	Description	Monitor for newly constructed network connections that are sent or received by untrusted hosts.

ID	Data source and component	Description
DS0029	Network Traffic: Network Traffic Flow	Monitor network data for uncommon data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious.
DS0029	Network Traffic: Network Traffic Content	Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).
DS0017	Command: Command Execution	Monitor executed commands and arguments that may steal data by exfiltrating it over a symmetrically encrypted network protocol other than that of the existing command and control channel.
DS0022	File: File Access	Monitor files viewed in isolation that may steal data by exfiltrating it over a symmetrically encrypted network protocol other than that of the existing command and control channel.
DS0029	Network Traffic: Network Connection Creation	Monitor for newly constructed network connections that are sent or received by untrusted hosts.

Mitigation

ID	M1057	Name	Data Loss Prevention	Description	Data loss prevention can detect and block sensitive data being uploaded via web browsers.

ID	M1031	Name	Network Intrusion Prevention	Description	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.

ID	M1030	Name	Network Segmentation	Description	Follow best practices for network firewall configurations to allow only necessary ports and traffic to enter and exit the network.

ID	M1037	Name	Filter Network Traffic	Description	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.

ID	Name	Description
M1057	Data Loss Prevention	Data loss prevention can detect and block sensitive data being uploaded via web browsers.
M1031	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.
M1030	Network Segmentation	Follow best practices for network firewall configurations to allow only necessary ports and traffic to enter and exit the network.
M1037	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.