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.
Limit Access to Resource Over Network: Restrict access to network resources, such as file shares, remote systems, and services, to only those users, accounts, or systems with a legitimate business requirement. This can include employing technologies like network concentrators, RDP gateways, and zero-trust network access (ZTNA) models, alongside hardening services and protocols. This mitigation can be implemented through the following measures:
Audit and Restrict Access:
- Regularly audit permissions for file shares, network services, and remote access tools.
- Remove unnecessary access and enforce least privilege principles for users and services.
- Use Active Directory and IAM tools to restrict access based on roles and attributes.
Deploy Secure Remote Access Solutions:
- Use RDP gateways, VPN concentrators, and ZTNA solutions to aggregate and secure remote access connections.
- Configure access controls to restrict connections based on time, device, and user identity.
- Enforce MFA for all remote access mechanisms.
Disable Unnecessary Services:
- Identify running services using tools like netstat (Windows/Linux) or Nmap.
- Disable unused services, such as Telnet, FTP, and legacy SMB, to reduce the attack surface.
- Use firewall rules to block traffic on unused ports and protocols.
Network Segmentation and Isolation:
- Use VLANs, firewalls, or micro-segmentation to isolate critical network resources from general access.
- Restrict communication between subnets to prevent lateral movement.
Monitor and Log Access:
- Monitor access attempts to file shares, RDP, and remote network resources using SIEM tools.
- Enable auditing and logging for successful and failed attempts to access restricted resources.
Tools for Implementation
File Share Management:
- Microsoft Active Directory Group Policies
- Samba (Linux/Unix file share management)
- AccessEnum (Windows access auditing tool)
Secure Remote Access:
- Microsoft Remote Desktop Gateway
- Apache Guacamole (open-source RDP/VNC gateway)
- Zero Trust solutions: Tailscale, Cloudflare Zero Trust
Service and Protocol Hardening:
- Nmap or Nessus for network service discovery
- Windows Group Policy Editor for disabling SMBv1, Telnet, and legacy protocols
- iptables or firewalld (Linux) for blocking unnecessary traffic
Network Segmentation:
- pfSense for open-source network isolation
User Account Management: User Account Management involves implementing and enforcing policies for the lifecycle of user accounts, including creation, modification, and deactivation. Proper account management reduces the attack surface by limiting unauthorized access, managing account privileges, and ensuring accounts are used according to organizational policies. This mitigation can be implemented through the following measures:
Enforcing the Principle of Least Privilege
- Implementation: Assign users only the minimum permissions required to perform their job functions. Regularly audit accounts to ensure no excess permissions are granted.
- Use Case: Reduces the risk of privilege escalation by ensuring accounts cannot perform unauthorized actions.
Implementing Strong Password Policies
- Implementation: Enforce password complexity requirements (e.g., length, character types). Require password expiration every 90 days and disallow password reuse.
- Use Case: Prevents adversaries from gaining unauthorized access through password guessing or brute force attacks.
Managing Dormant and Orphaned Accounts
- Implementation: Implement automated workflows to disable accounts after a set period of inactivity (e.g., 30 days). Remove orphaned accounts (e.g., accounts without an assigned owner) during regular account audits.
- Use Case: Eliminates dormant accounts that could be exploited by attackers.
Account Lockout Policies
- Implementation: Configure account lockout thresholds (e.g., lock accounts after five failed login attempts). Set lockout durations to a minimum of 15 minutes.
- Use Case: Mitigates automated attack techniques that rely on repeated login attempts.
Multi-Factor Authentication (MFA) for High-Risk Accounts
- Implementation: Require MFA for all administrative accounts and high-risk users. Use MFA mechanisms like hardware tokens, authenticator apps, or biometrics.
- Use Case: Prevents unauthorized access, even if credentials are stolen.
Restricting Interactive Logins
- Implementation: Restrict interactive logins for privileged accounts to specific secure systems or management consoles. Use group policies to enforce logon restrictions.
- Use Case: Protects sensitive accounts from misuse or exploitation.
Tools for Implementation
Built-in Tools:
- Microsoft Active Directory (AD): Centralized account management and RBAC enforcement.
- Group Policy Object (GPO): Enforce password policies, logon restrictions, and account lockout policies.
Identity and Access Management (IAM) Tools:
- Okta: Centralized user provisioning, MFA, and SSO integration.
- Microsoft Azure Active Directory: Provides advanced account lifecycle management, role-based access, and conditional access policies.
Privileged Account Management (PAM):
- CyberArk, BeyondTrust, Thycotic: Manage and monitor privileged account usage, enforce session recording, and JIT access.