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.

ID: M1037

Version: 1.2

Created: 11 June 2019

Last Modified: 11 December 2024

Version Permalink

Live Version

Techniques Addressed by Mitigation

Domain	ID		Name	Use
Enterprise	T1557		Adversary-in-the-Middle	Use network appliances and host-based security software to block network traffic that is not necessary within the environment, such as legacy protocols that may be leveraged for AiTM conditions.
		.001	LLMNR/NBT-NS Poisoning and SMB Relay	Use host-based security software to block LLMNR/NetBIOS traffic. Enabling SMB Signing can stop NTLMv2 relay attacks.^[1]^[2]^[3]
		.002	ARP Cache Poisoning	Consider enabling DHCP Snooping and Dynamic ARP Inspection on switches to create mappings between IP addresses requested via DHCP and ARP tables and tie the values to a port on the switch that may block bogus traffic.^[4]^[5]
		.003	DHCP Spoofing	Consider filtering DHCP traffic on ports 67 and 68 to/from unknown or untrusted DHCP servers. Additionally, port security may also be enabled on layer switches. Furthermore, consider enabling DHCP snooping on layer 2 switches as it will prevent DHCP spoofing attacks and starvation attacks. Consider tracking available IP addresses through a script or a tool. Additionally, block DHCPv6 traffic and incoming router advertisements, especially if IPv6 is not commonly used in the network.^[6]
Enterprise	T1071		Application Layer Protocol	Use network appliances to filter ingress or egress traffic and perform protocol-based filtering. Configure software on endpoints to filter network traffic.
		.004	DNS	Consider filtering DNS requests to unknown, untrusted, or known bad domains and resources. Resolving DNS requests with on-premise/proxy servers may also disrupt adversary attempts to conceal data within DNS packets.
		.005	Publish/Subscribe Protocols	Consider filtering publish/subscribe protocol requests to untrusted or known bad resources over irregular ports (e.g. MQTT’s standard ports are 1883 or 8883).
Enterprise	T1197		BITS Jobs	Modify network and/or host firewall rules, as well as other network controls, to only allow legitimate BITS traffic.
Enterprise	T1530		Data from Cloud Storage	Cloud service providers support IP-based restrictions when accessing cloud resources. Consider using IP allowlisting along with user account management to ensure that data access is restricted not only to valid users but only from expected IP ranges to mitigate the use of stolen credentials to access data.
Enterprise	T1602		Data from Configuration Repository	Apply extended ACLs to block unauthorized protocols outside the trusted network.^[7]
		.001	SNMP (MIB Dump)	Apply extended ACLs to block unauthorized protocols outside the trusted network.^[7]
		.002	Network Device Configuration Dump	Apply extended ACLs to block unauthorized protocols outside the trusted network.^[7]
Enterprise	T1499		Endpoint Denial of Service	Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services.^[8] Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport. To defend against SYN floods, enable SYN Cookies.
		.001	OS Exhaustion Flood	Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services.^[8] Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport. To defend against SYN floods, enable SYN Cookies.
		.002	Service Exhaustion Flood	Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services.^[8] Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport.
		.003	Application Exhaustion Flood	Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services.^[8] Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport.
		.004	Application or System Exploitation	Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services.^[8] Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport.
Enterprise	T1048		Exfiltration Over Alternative Protocol	Enforce proxies and use dedicated servers for services such as DNS and only allow those systems to communicate over respective ports/protocols, instead of all systems within a network. Cloud service providers support IP-based restrictions when accessing cloud resources. Consider using IP allowlisting along with user account management to ensure that data access is restricted not only to valid users but only from expected IP ranges to mitigate the use of stolen credentials to access data.
		.001	Exfiltration Over Symmetric Encrypted Non-C2 Protocol	Enforce proxies and use dedicated servers for services such as DNS and only allow those systems to communicate over respective ports/protocols, instead of all systems within a network.
		.002	Exfiltration Over Asymmetric Encrypted Non-C2 Protocol	Enforce proxies and use dedicated servers for services such as DNS and only allow those systems to communicate over respective ports/protocols, instead of all systems within a network.
		.003	Exfiltration Over Unencrypted Non-C2 Protocol	Enforce proxies and use dedicated servers for services such as DNS and only allow those systems to communicate over respective ports/protocols, instead of all systems within a network.
Enterprise	T1187		Forced Authentication	Block SMB traffic from exiting an enterprise network with egress filtering or by blocking TCP ports 139, 445 and UDP port 137. Filter or block WebDAV protocol traffic from exiting the network. If access to external resources over SMB and WebDAV is necessary, then traffic should be tightly limited with allowlisting. ^[9] ^[10]
Enterprise	T1570		Lateral Tool Transfer	Consider using the host firewall to restrict file sharing communications such as SMB. ^[11]
Enterprise	T1599		Network Boundary Bridging	Upon identifying a compromised network device being used to bridge a network boundary, block the malicious packets using an unaffected network device in path, such as a firewall or a router that has not been compromised. Continue to monitor for additional activity and to ensure that the blocks are indeed effective.
		.001	Network Address Translation Traversal	Block Traffic Upon identifying a compromised network device being used to bridge a network boundary, block the malicious packets using an unaffected network device in path, such as a firewall or a router that has not been compromised. Continue to monitor for additional activity and to ensure that the blocks are indeed effective.
Enterprise	T1498		Network Denial of Service	When flood volumes exceed the capacity of the network connection being targeted, it is typically necessary to intercept the incoming traffic upstream to filter out the attack traffic from the legitimate traffic. Such defenses can be provided by the hosting Internet Service Provider (ISP) or by a 3rd party such as a Content Delivery Network (CDN) or providers specializing in DoS mitigations.^[8] Depending on flood volume, on-premises filtering may be possible by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport.^[8] As immediate response may require rapid engagement of 3rd parties, analyze the risk associated to critical resources being affected by Network DoS attacks and create a disaster recovery plan/business continuity plan to respond to incidents.^[8]
		.001	Direct Network Flood	When flood volumes exceed the capacity of the network connection being targeted, it is typically necessary to intercept the incoming traffic upstream to filter out the attack traffic from the legitimate traffic. Such defenses can be provided by the hosting Internet Service Provider (ISP) or by a 3rd party such as a Content Delivery Network (CDN) or providers specializing in DoS mitigations.^[8] Depending on flood volume, on-premises filtering may be possible by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport.^[8] As immediate response may require rapid engagement of 3rd parties, analyze the risk associated to critical resources being affected by Network DoS attacks and create a disaster recovery plan/business continuity plan to respond to incidents.^[8]
		.002	Reflection Amplification	When flood volumes exceed the capacity of the network connection being targeted, it is typically necessary to intercept the incoming traffic upstream to filter out the attack traffic from the legitimate traffic. Such defenses can be provided by the hosting Internet Service Provider (ISP) or by a 3rd party such as a Content Delivery Network (CDN) or providers specializing in DoS mitigations.^[8] Depending on flood volume, on-premises filtering may be possible by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport.^[8] As immediate response may require rapid engagement of 3rd parties, analyze the risk associated to critical resources being affected by Network DoS attacks and create a disaster recovery plan/business continuity plan to respond to incidents.^[8]
Enterprise	T1095		Non-Application Layer Protocol	Filter network traffic to prevent use of protocols across the network boundary that are unnecessary. If VMCI is not required in ESXi environments, consider restricting guest virtual machines from accessing VMCI services.^[12]
Enterprise	T1572		Protocol Tunneling	Consider filtering network traffic to untrusted or known bad domains and resources.
Enterprise	T1090		Proxy	Traffic to known anonymity networks and C2 infrastructure can be blocked through the use of network allow and block lists. It should be noted that this kind of blocking may be circumvented by other techniques like Domain Fronting.
		.003	Multi-hop Proxy	Traffic to known anonymity networks and C2 infrastructure can be blocked through the use of network allow and block lists. It should be noted that this kind of blocking may be circumvented by other techniques like Domain Fronting.
Enterprise	T1219		Remote Access Tools	Properly configure firewalls, application firewalls, and proxies to limit outgoing traffic to sites and services used by remote access software.
		.002	Remote Desktop Software	Properly configure firewalls, application firewalls, and proxies to limit outgoing traffic to sites and services used by remote access software.
Enterprise	T1021	.002	Remote Services: SMB/Windows Admin Shares	Consider using the host firewall to restrict file sharing communications such as SMB. ^[11]
		.005	Remote Services: VNC	VNC defaults to TCP ports 5900 for the server, 5800 for browser access, and 5500 for a viewer in listening mode. Filtering or blocking these ports will inhibit VNC traffic utilizing default ports.
Enterprise	T1218		System Binary Proxy Execution	Use network appliances to filter ingress or egress traffic and perform protocol-based filtering. Configure software on endpoints to filter network traffic.
		.012	Verclsid	Consider modifying host firewall rules to prevent egress traffic from verclsid.exe.
Enterprise	T1205		Traffic Signaling	Mitigation of some variants of this technique could be achieved through the use of stateful firewalls, depending upon how it is implemented.
		.001	Port Knocking	Mitigation of some variants of this technique could be achieved through the use of stateful firewalls, depending upon how it is implemented.
		.002	Socket Filters	Mitigation of some variants of this technique could be achieved through the use of stateful firewalls, depending upon how it is implemented.
Enterprise	T1537		Transfer Data to Cloud Account	Implement network-based filtering restrictions to prohibit data transfers to untrusted VPCs.
Enterprise	T1552		Unsecured Credentials	Limit access to the Instance Metadata API. A properly configured Web Application Firewall (WAF) may help prevent external adversaries from exploiting Server-side Request Forgery (SSRF) attacks that allow access to the Cloud Instance Metadata API.^[13]
		.005	Cloud Instance Metadata API	Limit access to the Instance Metadata API. A properly configured Web Application Firewall (WAF) may help prevent external adversaries from exploiting Server-side Request Forgery (SSRF) attacks that allow access to the Cloud Instance Metadata API.^[13]

Filter Network Traffic

Enterprise Layer

Techniques Addressed by Mitigation

References