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Curriculum lobby
0s40 min Loop40 min★ 170 XP
Syllabus

Network Security Essentials

Networking Fundamentals for SecurityOSI Model Deep Dive (Layers 1–7) & Security RelevanceTCP/IP Suite Architecture (Link, Internet, Transport, Application)Key Protocols: ARP, IP, ICMP, TCP, UDP, DNS, HTTP/HTTPSIPv4 vs. IPv6 Security ImplicationsNetwork Addressing, Subnetting, and CIDR (Security Zoning Perspective)
TCP/IP Vulnerabilities & AttacksTCP Attacks (SYN Flood, Session Hijacking, Sequence Prediction)UDP Attacks (UDP Flood, Port Scan Evasion)IP Spoofing & Source Routing ExploitsARP Spoofing / ARP Poisoning (Man-in-the-Middle)ICMP Attacks (Ping of Death, Smurf, Tunneling)DNS Attacks (Cache Poisoning, DNS Spoofing, and Tunneling)Layer 2 Attacks (MAC Flooding, CAM Table Overflow, STP Manipulation)Sniffing & Eavesdropping (Promiscuous Mode, Wireshark Countermeasures)
Firewalls – First Line of DefenseFirewall Types: Packet Filtering (Stateless) vs. Stateful InspectionNext-Generation Firewalls (NGFW): Application Awareness, IPS IntegrationFirewall Rule Structure (Source, Destination, Port, Action)Default-Deny vs. Default-Permit PoliciesImplementing Firewall Zones (WAN, LAN, DMZ)Network Address Translation (NAT) Security Benefits & LimitationsOpen-Source Firewalls (iptables, nftables, pfSense, and OPNsense)Enterprise Firewalls (Cisco, Palo Alto, and Fortinet Concepts)
Intrusion Detection & Prevention Systems (IDS/IPS)IDS vs. IPS vs. HIDS vs. NIDSSignature-Based vs. Anomaly-Based vs. Policy-Based DetectionSnort Fundamentals (Rules, Preprocessors, and Output Plugins)Suricata (Multi-threading, Protocol Analysis, and TLS Fingerprinting)Zeek (formerly Bro) for Network Analysis and Metadata LoggingWriting Custom IDS Rules (Detecting Scanning and Suspicious Activity)Evasion Techniques (Fragmentation, Encryption, and Polymorphism)IDS/IPS Placement (In-Line vs. Passive, SPAN Ports vs. TAPs)
VPNs – Secure Remote ConnectivityVPN Purpose & Use Cases (Remote Access vs. Site-to-Site)Tunneling Protocols: PPTP (Insecure), L2TP/IPsec, OpenVPN, WireGuardIPsec Deep Dive (AH vs. ESP, Transport vs. Tunnel Mode, IKE Phases)SSL/TLS VPNs (Browser-Based vs. Full Tunnel)WireGuard Architecture (Simpler, Faster, Modern Crypto)VPN Split Tunneling vs. Full Tunneling (Security Trade-offs)Common VPN Misconfigurations & Leak Testing (DNS, WebRTC, IPv6)Enterprise VPN Solutions (Cisco AnyConnect, Pulse Secure, FortiClient)
Network Segmentation & ZoningWhy Segment? (Breach Containment, Performance, Compliance)VLANs (Tagged/Untagged, VLAN Hopping Attacks)DMZ Design (Single-Homed, Dual-Homed, Multi-Tier)Microsegmentation (Software-Defined Networking, Zero Trust)Internal Network Segmentation (Corporate vs. Production vs. Guest)Jump Boxes / Bastion Hosts for Administrative AccessAir-Gapped Networks & Data Diode ConceptsSegmenting Cloud VPCs (AWS Security Groups, Azure NSGs)
Network Hardening & Best PracticesDisabling Unnecessary Ports & ServicesHardening Router & Switch Configurations (SSH v2, Disable Telnet)Port Security (MAC Limiting, Sticky MAC, 802.1X)DHCP Snooping, Dynamic ARP Inspection (DAI), IP Source GuardControl Plane Policing (CoPP) & Management Plane ProtectionLogging & Monitoring (Syslog, NetFlow, IPFIX, sFlow)Nmap for Internal Auditing & Verification
Secure Network Design & ArchitectureDefense-in-Depth for NetworksZero Trust Network Access (ZTNA) vs. Traditional VPNSecure Access Service Edge (SASE) FrameworkRedundancy & High Availability (Failover Clusters, Load Balancers)Network Segmentation for Compliance (PCI DSS, HIPAA, NIST 800-171)
Real-World Network Attacks & DefensesRansomware Lateral Movement (How Segmentation Stops It)DNS Tunneling Detection & PreventionInternal Reconnaissance Defense (Honeypots, Canary Tokens)Case Study: SolarWinds & Network Detection Gaps
Hands-On LabsConfiguring iptables Rules for a Linux GatewaySetting Up Snort/Suricata & Alerting on ScansBuilding an L2TP/IPsec VPN (StrongSwan or LibreSwan)VLAN Segmentation Practice (Cisco Packet Tracer / EVE-NG)ARP Spoofing Detection & Prevention ExerciseFirewall Rule Audit & Optimization Project
network-security-essentials / vpn-purpose-use-cases

VPN Purpose & Use Cases (Remote Access vs. Site-to-Site)

#Extending the Trust Boundary: VPN Fundamentals#link

Virtual Private Networks (VPNs) create encrypted tunnels over untrusted networks, effectively extending the local network to remote users or branch offices. Understanding the architectural differences between remote access and site-to-site is foundational.

Remote Access VPNs (Client-to-Site)

Used by individual employees connecting from home or public Wi-Fi. The client software authenticates the user, and the tunnel terminates at the corporate gateway, granting the endpoint access to internal resources.

info

💡 Pro-tip: Never grant remote access VPN users full network access by default. Implement Network Access Control (NAC) to restrict tunnel endpoints to only the specific subnets required for their role.

Checking Active OpenVPN Sessions
root@vulnarex:~#cat /etc/openvpn/openvpn-status.log | grep '192.168.1'

This log shows a remote user (198.51.100.5) assigned an internal tunnel IP (10.8.0.2), mapping their remote identity to an internal network identity.

Site-to-Site VPNs (Gateway-to-Gateway)

Connects entire networks (e.g., HQ to a branch office). The tunnel is established between two routers/firewalls. Endpoints on both sides are unaware of the encryption; routing tables simply point traffic into the tunnel.

STRICT SECURE AUDIT RULE

⚠️ Site-to-Site VPNs can inadvertently create routing loops or backdoor paths if overlapping subnets (e.g., 192.168.1.0/24 on both sides) are not carefully managed and NAT'd.

TypeInitiatorUse Case
Remote AccessEndpoint ClientTelecommuting / Mobile
Site-to-SiteEdge RouterBranch Office Connectivity
SSL PortalWeb BrowserVendor / Limited Access
  • ▪Define access policies per user role
  • ▪Avoid overlapping IP spaces in S2S
  • ▪Implement MFA for Remote Access
  • ▪Monitor tunnel uptime and throughput
quiz BLOCK (★ 50 XP)

In a Site-to-Site VPN, which device handles the encryption and decryption of traffic?

Select your proof vectors above

Verification Proof Checkpoint

Verify exercises to earn ★ 170 XP and unlock next lab level.

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Lab Notes

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Checkpoints
Extending the Trust Boundary: VPN Fundamentals
Laboratory Sanity Code

Isolate active probes on matched virtual networks. Keep execution streams fully sandboxed.