T1599: Network Boundary Bridging

Data from MITRE ATT&CK®:

Adversaries may bridge network boundaries by compromising perimeter network devices or internal devices responsible for network segmentation. Breaching these devices may enable an adversary to bypass restrictions on traffic routing that otherwise separate trusted and untrusted networks.

Devices such as routers and firewalls can be used to create boundaries between trusted and untrusted networks. They achieve this by restricting traffic types to enforce organizational policy in an attempt to reduce the risk inherent in such connections. Restriction of traffic can be achieved by prohibiting IP addresses, layer 4 protocol ports, or through deep packet inspection to identify applications. To participate with the rest of the network, these devices can be directly addressable or transparent, but their mode of operation has no bearing on how the adversary can bypass them when compromised.

When an adversary takes control of such a boundary device, they can bypass its policy enforcement to pass normally prohibited traffic across the trust boundary between the two separated networks without hinderance. By achieving sufficient rights on the device, an adversary can reconfigure the device to allow the traffic they want, allowing them to then further achieve goals such as command and control via Multi-hop Proxy or exfiltration of data via Traffic Duplication. Adversaries may also target internal devices responsible for network segmentation and abuse these in conjunction with Internal Proxy to achieve the same goals.(Citation: Kaspersky ThreatNeedle Feb 2021) In the cases where a border device separates two separate organizations, the adversary can also facilitate lateral movement into new victim environments.

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Privileged Account Management

Manage the creation, modification, use, and permissions associated to privileged accounts, including SYSTEM and root.

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.

Multi-factor Authentication

Use two or more pieces of evidence to authenticate to a system; such as username and password in addition to a token from a physical smart card or token generator.

Password Policies

Set and enforce secure password policies for accounts.

Credential Access Protection

Use capabilities to prevent successful credential access by adversaries; including blocking forms of credential dumping.

Network Traffic Content (Network Traffic)

Logged network traffic data showing both protocol header and body values (ex: PCAP)

Network Traffic Flow (Network Traffic)

Summarized network packet data, with metrics, such as protocol headers and volume (ex: Netflow or Zeek http.log)