Adversaries may use port knocking to hide open ports used for persistence or command and control. To enable a port, an adversary sends a series of attempted connections to a predefined sequence of closed ports. After the sequence is completed, opening a port is often accomplished by the host based firewall, but could also be implemented by custom software.
This technique has been observed both for the dynamic opening of a listening port as well as the initiating of a connection to a listening server on a different system.
The observation of the signal packets to trigger the communication can be conducted through different methods. One means, originally implemented by Cd00r (Citation: Hartrell cd00r 2002), is to use the libpcap libraries to sniff for the packets in question. Another method leverages raw sockets, which enables the malware to use ports that are already open for use by other programs.
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| UEM-10 | Software Firewall | mitigates | T1205.001 | Port Knocking |
Comments
This control describes how CSPs and CSCs must install, update, and properly configure endpoint and software-defined firewalls, regularly review and approve firewall rule changes, and monitor traffic for anomalies and malicious code. These mitigative actions help prevent unauthorized access, block threats, and ensure only approved firewall rules are active.
References
|