type: attack-pattern
spec_version: 2.1
id: attack-pattern--c21d5a77-d422-4a69-acd7-2c53c1faa34b
created: 2017-05-31T21:31:10.728Z
created_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
revoked: no
external_references: source_name: mitre-attack
url: https://attack.mitre.org/techniques/T1095
external_id: T1095
source_name: Google Cloud Threat Intelligence VMWare ESXi Zero-Day 2023
description: Alexander Marvi, Brad Slaybaugh, Ron Craft, and Rufus Brown. (2023, June 13). VMware ESXi Zero-Day Used by Chinese Espionage Actor to Perform Privileged Guest Operations on Compromised Hypervisors. Retrieved March 26, 2025.
url: https://cloud.google.com/blog/topics/threat-intelligence/vmware-esxi-zero-day-bypass/
source_name: University of Birmingham C2
description: Gardiner, J., Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.
url: https://arxiv.org/ftp/arxiv/papers/1408/1408.1136.pdf
source_name: Cisco Synful Knock Evolution
description: Graham Holmes. (2015, October 8). Evolution of attacks on Cisco IOS devices. Retrieved October 19, 2020.
url: https://blogs.cisco.com/security/evolution-of-attacks-on-cisco-ios-devices
source_name: Microsoft ICMP
description: Microsoft. (n.d.). Internet Control Message Protocol (ICMP) Basics. Retrieved December 1, 2014.
url: http://support.microsoft.com/KB/170292
source_name: Cisco Blog Legacy Device Attacks
description: Omar Santos. (2020, October 19). Attackers Continue to Target Legacy Devices. Retrieved October 20, 2020.
url: https://community.cisco.com/t5/security-blogs/attackers-continue-to-target-legacy-devices/ba-p/4169954
source_name: Wikipedia OSI
description: Wikipedia. (n.d.). List of network protocols (OSI model). Retrieved December 4, 2014.
url: http://en.wikipedia.org/wiki/List_of_network_protocols_%28OSI_model%29
object_marking_refs: marking-definition--fa42a846-8d90-4e51-bc29-71d5b4802168
modified: 2025-10-24T17:49:20.136Z
name: Non-Application Layer Protocol
description: Adversaries may use an OSI non-application layer protocol for communication between host and C2 server or among infected hosts within a network. The list of possible protocols is extensive.(Citation: Wikipedia OSI) Specific examples include use of network layer protocols, such as the Internet Control Message Protocol (ICMP), transport layer protocols, such as the User Datagram Protocol (UDP), session layer protocols, such as Socket Secure (SOCKS), as well as redirected/tunneled protocols, such as Serial over LAN (SOL).

ICMP communication between hosts is one example.(Citation: Cisco Synful Knock Evolution) Because ICMP is part of the Internet Protocol Suite, it is required to be implemented by all IP-compatible hosts.(Citation: Microsoft ICMP) However, it is not as commonly monitored as other Internet Protocols such as TCP or UDP and may be used by adversaries to hide communications.

In ESXi environments, adversaries may leverage the Virtual Machine Communication Interface (VMCI) for communication between guest virtual machines and the ESXi host. This traffic is similar to client-server communications on traditional network sockets but is localized to the physical machine running the ESXi host, meaning it does not traverse external networks (routers, switches). This results in communications that are invisible to external monitoring and standard networking tools like tcpdump, netstat, nmap, and Wireshark. By adding a VMCI backdoor to a compromised ESXi host, adversaries may persistently regain access from any guest VM to the compromised ESXi host’s backdoor, regardless of network segmentation or firewall rules in place.(Citation: Google Cloud Threat Intelligence VMWare ESXi Zero-Day 2023)
kill_chain_phases: kill_chain_name: mitre-attack
phase_name: command-and-control
x_mitre_attack_spec_version: 3.2.0
x_mitre_contributors: Ryan Becwar
Duane Michael
x_mitre_deprecated: no
x_mitre_domains: enterprise-attack
x_mitre_is_subtechnique: no
x_mitre_modified_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
x_mitre_platforms: ESXi
Linux
macOS
Network Devices
Windows
x_mitre_version: 2.4