- Tactics
- stealth , Persistence , Command and Control
- Platforms
- Linux, macOS, Network Devices, Windows
- Reference
- attack.mitre.org/techniques/T1205.001
Description
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.
How GTK Cyber trains on this
GTK Cyber's hands-on training programs cover detection engineering across the MITRE ATT&CK framework, including the stealth, Persistence, Command and Control tactic this technique falls under. Our practitioner-led courses focus on building real detections, not just memorizing technique IDs.
Related techniques
- T1001 — Data Obfuscation
- T1006 — Direct Volume Access
- T1008 — Fallback Channels
- T1014 — Rootkit
- T1027 — Obfuscated Files or Information
- T1036 — Masquerading
- T1037 — Boot or Logon Initialization Scripts
- T1053 — Scheduled Task/Job
- T1055 — Process Injection
- T1070 — Indicator Removal
- T1071 — Application Layer Protocol
- T1078 — Valid Accounts