Sub-technique of T1205 Traffic Signaling.View on attack.mitre.org
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 , 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.
Rules on DetectionCode tagged with T1205.001.
None recorded.
| Used by | Procedure example |
|---|---|
| GroupPROMETHIUM | PROMETHIUM has used a script that configures the knockd service and firewall to only accept C2 connections from systems that use a specified sequence of knock ports. |
| GroupUNC3886 | UNC3886 maintained persistence on FortiGate Firewalls through ICMP port knocking. |
| Used by | Procedure example |
|---|---|
| Malwarecd00r | cd00r can monitor for a single TCP-SYN packet to be sent in series to a configurable set of ports (200, 80, 22, 53 and 3 in the original code) before opening a port for communication. |
| MalwareMafalda | Mafalda can use port-knocking to authenticate itself to another implant called Cryshell to establish an indirect connection to the C2 server. |
| MalwaremetaMain | metaMain has authenticated itself to a different implant, Cryshell, through a port knocking and handshake procedure. |
| MalwareREPTILE | REPTILE has the ability to control compromised endpoints via port knocking. |
Data from MITRE ATT&CK® (Enterprise). ATT&CK® is a registered trademark of The MITRE Corporation.
