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)

Linked Issues

Issuelinks
Linktyp Issue
is related to Techniques
is blocked by Network Intrusion Prevention
is blocked by Audit
is blocked by Filter Network Traffic
is blocked by Network Segmentation
is blocked by Detection of Non-Application Layer Protocols for C2
is blocked by Security, Compliance & Resilience Controls Oversight
is blocked by Secure Baseline Configurations
is blocked by Least Functionality
is blocked by Continuous Monitoring
is blocked by Malicious Code Protection (Anti-Malware)
is blocked by Access Enforcement
is blocked by Boundary Protection
is blocked by Data Flow Enforcement – Access Control Lists (ACLs)
is blocked by Information Output Filtering
is blocked by Input Data Validation
Impressum Deutsch Englisch