Protocol Tunneling
Adversaries may tunnel network communications to and from a victim system within a separate protocol to avoid detection/network filtering and/or enable access to otherwise unreachable systems. Tunneling involves explicitly encapsulating a protocol within another. This behavior may conceal malicious traffic by blending in with existing traffic and/or provide an outer layer of encryption (similar to a VPN). Tunneling could also enable routing of network packets that would otherwise not reach their intended destination, such as SMB, RDP, or other traffic that would be filtered by network appliances or not routed over the Internet. There are various means to encapsulate a protocol within another protocol. For example, adversaries may perform SSH tunneling (also known as SSH port forwarding), which involves forwarding arbitrary data over an encrypted SSH tunnel. Protocol Tunneling may also be abused by adversaries during Dynamic Resolution. Known as DNS over HTTPS (DoH), queries to resolve C2 infrastructure may be encapsulated within encrypted HTTPS packets. Adversaries may also leverage Protocol Tunneling in conjunction with Proxy and/or Protocol or Service Impersonation to further conceal C2 communications and infrastructure.
Open detection, hunting, mitigation, and evidence workspace
Detection logic
Monitoring for systems listening and/or establishing external connections using ports/protocols commonly associated with tunneling, such as SSH (port 22). Also monitor for processes commonly associated with tunneling, such as Plink and the OpenSSH client. Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Analyze packet contents to detect application layer protocols that do not follow the expected protocol standards regarding syntax, structure, or any other variable adversaries could leverage to conceal data.
Observed actors
Correlated CTI and IR reports
FBI / CISA / DC3 · direct source mapping1. Executive Summary
Israel Threat Actors CTI · explicit report mentionOilRig (APT34 / Helix Kitten / Earth Simnavaz etc)
Israel Threat Actors CTI · explicit report mentionPioneer Kitten (Fox Kitten, Lemon Sandstorm, UNC757) – Actor Deep Research
Israel Threat Actors CTI · explicit report mention