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Curriculum lobby
0s45 min Loop45 min★ 220 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 / jump-boxes-bastion-hosts

Jump Boxes / Bastion Hosts for Administrative Access

#The Airlock for Administrators: Bastion Hosts#link

Administrators require privileged access to critical infrastructure. Exposing SSH or RDP ports directly to the internet or corporate network is a massive risk. Jump boxes (Bastion hosts) act as heavily fortified, audited gateways for all administrative sessions.

Architecture of a Bastion Host

A bastion host sits in a dedicated management zone. It is the only system allowed to initiate administrative connections to production servers. All admin traffic is funneled through this single choke point, enabling strict MFA and session recording.

info

💡 Pro-tip: Disable all direct SSH/RDP access on production servers. Configure their host firewalls to ONLY accept management connections from the specific IP address of the Bastion host.

SSH via Bastion (ProxyJump)
root@vulnarex:~#ssh -J admin@bastion.vulnarex.com root@db-server.internal

The -J flag routes the SSH connection through the bastion host securely, ensuring the admin never directly exposes their client to the internal production network.

Session Recording and Audit

Modern bastion solutions (like CyberArk or Apache Guacamole) record the entire terminal session or GUI screen. This provides an immutable audit trail of exactly what commands an administrator executed during an incident.

STRICT SECURE AUDIT RULE

⚠️ The bastion host is the crown jewel. If an attacker compromises the bastion, they own the entire infrastructure. Harden it relentlessly: disable root login, enforce hardware MFA, and restrict outbound internet access.

FeatureStandard SSHBastion Host
Access ControlIP basedIdentity + MFA
Audit TrailSyslog onlyFull Session Recording
Attack SurfaceEvery serverSingle hardened host
  • ▪Deploy a dedicated management zone
  • ▪Enforce MFA on all bastion logins
  • ▪Record all administrative sessions
  • ▪Block direct admin ports on targets
quiz BLOCK (★ 50 XP)

What is the primary security benefit of forcing all admin traffic through a Bastion host?

Select your proof vectors above

Verification Proof Checkpoint

Verify exercises to earn ★ 220 XP and unlock next lab level.

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Checkpoints
The Airlock for Administrators: Bastion Hosts
Laboratory Sanity Code

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