LLMNR/NBT-NS Poisoning and SMB Relay

Detect LLMNR/NBT-NS Poisoning and SMB Relay on Windows

Disable or Remove Feature or Program: Disable or remove unnecessary and potentially vulnerable software, features, or services to reduce the attack surface and prevent abuse by adversaries. This involves identifying software or features that are no longer needed or that could be exploited and ensuring they are either removed or properly disabled. This mitigation can be implemented through the following measures:

Remove Legacy Software:

• Use Case: Disable or remove older versions of software that no longer receive updates or security patches (e.g., legacy Java, Adobe Flash).
• Implementation: A company removes Flash Player from all employee systems after it has reached its end-of-life date.

Disable Unused Features:

• Use Case: Turn off unnecessary operating system features like SMBv1, Telnet, or RDP if they are not required.
• Implementation: Disable SMBv1 in a Windows environment to mitigate vulnerabilities like EternalBlue.

Control Applications Installed by Users:

• Use Case: Prevent users from installing unauthorized software via group policies or other management tools.
• Implementation: Block user installations of unauthorized file-sharing applications (e.g., BitTorrent clients) in an enterprise environment.

Remove Unnecessary Services:

• Use Case: Identify and disable unnecessary default services running on endpoints, servers, or network devices.
• Implementation: Disable unused administrative shares (e.g., C$, ADMIN$) on workstations.

Restrict Add-ons and Plugins:

• Use Case: Remove or disable browser plugins and add-ons that are not needed for business purposes.
• Implementation: Disable Java and ActiveX plugins in web browsers to prevent drive-by attacks.

Network Intrusion Prevention: Use intrusion detection signatures to block traffic at network boundaries.

Network Segmentation: Network segmentation involves dividing a network into smaller, isolated segments to control and limit the flow of traffic between devices, systems, and applications. By segmenting networks, organizations can reduce the attack surface, restrict lateral movement by adversaries, and protect critical assets from compromise.

Effective network segmentation leverages a combination of physical boundaries, logical separation through VLANs, and access control policies enforced by network appliances like firewalls, routers, and cloud-based configurations. This mitigation can be implemented through the following measures:

Segment Critical Systems:

• Identify and group systems based on their function, sensitivity, and risk. Examples include payment systems, HR databases, production systems, and internet-facing servers.
• Use VLANs, firewalls, or routers to enforce logical separation.

Implement DMZ for Public-Facing Services:

• Host web servers, DNS servers, and email servers in a DMZ to limit their access to internal systems.
• Apply strict firewall rules to filter traffic between the DMZ and internal networks.

Use Cloud-Based Segmentation:

• In cloud environments, use VPCs, subnets, and security groups to isolate applications and enforce traffic rules.
• Apply AWS Transit Gateway or Azure VNet peering for controlled connectivity between cloud segments.

Apply Microsegmentation for Workloads:

• Use software-defined networking (SDN) tools to implement workload-level segmentation and prevent lateral movement.

Restrict Traffic with ACLs and Firewalls:

• Apply Access Control Lists (ACLs) to network devices to enforce "deny by default" policies.
• Use firewalls to restrict both north-south (external-internal) and east-west (internal-internal) traffic.

Monitor and Audit Segmented Networks:

• Regularly review firewall rules, ACLs, and segmentation policies.
• Monitor network flows for anomalies to ensure segmentation is effective.

Test Segmentation Effectiveness:

• Perform periodic penetration tests to verify that unauthorized access is blocked between network segments.

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.