T1205.001 Port Knocking — Attack Pattern

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.

MITRE ATT&CK Detection Strategies
1

DET0302 Port-knock → rule/daemon change → first successful connect (T1205.001)

AN0842 Windows

A remote source rapidly touches a short sequence of closed ports (SYN→RST/S0) on a Windows host. Within a short window the host changes firewall state (WFP rule added/modified or service starts listening) and then the same source completes the first successful handshake to the newly opened port.

WinEventLog:Sysmon WinEventLog:Sysmon WinEventLog:Microsoft-Windows-Windows Firewall With Advanced Security/Firewall

AN0844 macOS

A source performs a closed-port sequence; the endpoint enables a PF/socketfilterfw rule or a background process binds a port; then a successful connection completes from the same source.

macos:unifiedlog macos:unifiedlog NSM:Flow

AN0843 Linux

A source performs a short closed-port sequence; the host then modifies iptables/nftables/ufw rules or starts a daemon binding a new socket, followed by a successful connection from the same source.

auditd:SYSCALL auditd:SYSCALL NSM:Flow

+1 more analytics

MITRE ATT&CK Mitigations
1

M1037

Filter Network Traffic

Employ network appliances and endpoint software to filter ingress, egress, and lateral network traffic. This includes protocol-based filtering, enforcing firewall rules, and blocking or restricting traffic based on predefined conditions to limit adversary movement and data exfiltration. This mitigation can be implemented through the following measures: Ingress Traffic Filtering: - Use Case: Configure network firewalls to allow traffic only from authorized IP addresses to public-facing servers. - Implementation: Limit SSH (port 22) and RDP (port 3389) traffic to specific IP ranges. Egress Traffic Filtering: - Use Case: Use firewalls or endpoint security software to block unauthorized outbound traffic to prevent data exfiltration and command-and-control (C2) communications. - Implementation: Block outbound traffic to known malicious IPs or regions where communication is unexpected. Protocol-Based Filtering: - Use Case: Restrict the use of specific protocols that are commonly abused by adversaries, such as SMB, RPC, or Telnet, based on business needs. - Implementation: Disable SMBv1 on endpoints to prevent exploits like EternalBlue. Network Segmentation: - Use Case: Create network segments for critical systems and restrict communication between segments unless explicitly authorized. - Implementation: Implement VLANs to isolate IoT devices or guest networks from core business systems. Application Layer Filtering: - Use Case: Use proxy servers or Web Application Firewalls (WAFs) to inspect and block malicious HTTP/S traffic. - Implementation: Configure a WAF to block SQL injection attempts or other web application exploitation techniques.

Port Knocking

Description

MITRE ATT&CK Detection Strategies 1

MITRE ATT&CK Mitigations 1

Details

MITRE ATT&CK Detection Strategies
1

MITRE ATT&CK Mitigations
1