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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: 10 October 2019

Techniques Addressed by Mitigation

Domain ID Name Description
Enterprise T1197 BITS Jobs

Modify network and/or host firewall rules, as well as other network controls, to only allow legitimate BITS traffic.

Enterprise T1522 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.[7]

Enterprise T1094 Custom Command and Control Protocol

Filter network traffic to look for unusual or non-standard protocols.

Enterprise T1530 Data from Cloud Storage Object

Cloud service providers support IP-based restrictions when accessing cloud resources. Consider using IP whitelisting 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. 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.[1]

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.

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 whitelisting.[2][3]

Enterprise T1171 LLMNR/NBT-NS Poisoning and Relay

Use host-based security software to block LLMNR/NetBIOS traffic. Enabling SMB Signing can stop NTLMv2 relay attacks.[4][5][6]

Enterprise T1188 Multi-hop Proxy

Traffic to known anonymity networks and C2 infrastructure can be blocked through the use of network black and white lists. It should be noted that this kind of blocking may be circumvented by other techniques like Domain Fronting.

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.

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.

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][1][1]

Enterprise T1205 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 T1219 Remote Access Tools

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

Enterprise T1095 Standard Non-Application Layer Protocol

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

Enterprise T1537 Transfer Data to Cloud Account

Implement network-based filtering restrictions to prohibit data transfers to untrusted VPCs.

Enterprise T1078 Valid Accounts

Cloud service providers support IP-based restrictions when accessing cloud resources. Consider using IP whitelisting on cloud-based systems 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.

References