Filter Network Traffic

Use network appliances to filter ingress or egress traffic and perform protocol-based filtering. Configure software on endpoints to filter network traffic.

ID: M1037
Version: 1.1
Created: 11 June 2019
Last Modified: 20 June 2020

Techniques Addressed by Mitigation

Domain ID Name Use
Enterprise T1071 .004 Application Layer Protocol: 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.

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 Object

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 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.[1] 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.[1] 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.[1] 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.[1] 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.[1] 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.

.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/Obfuscated 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. [2] [3]

Enterprise T1570 Lateral Tool Transfer

Consider using the host firewall to restrict file sharing communications such as SMB. [8]

Enterprise T1557 Man-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 MiTM.

.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.[5][6][7]

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.[1]

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.[1]

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.[1]

.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.[1]

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.[1]

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.[1]

.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.[1]

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.[1]

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.[1]

Enterprise T1095 Non-Application Layer Protocol

Filter network traffic to prevent use of protocols across the network boundary that are unnecessary.

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 Software

Properly configure firewalls, application firewalls, and proxies to limit outgoing traffic to sites and services used by remote access tools.

Enterprise T1021 .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.

.002 Remote Services: SMB/Windows Admin Shares

Consider using the host firewall to restrict file sharing communications such as SMB. [8]

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.

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 using a host-based firewall such as iptables. 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.[4]

.005 Cloud Instance Metadata API

Limit access to the Instance Metadata API using a host-based firewall such as iptables. 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.[4]

References