Defensive › Module 1 › Lesson 3
Your Hosts Only
Your lab lives at $LAB_HOST on YOUR hardware — never stranger subnets or shared café gear.
Visual · defense_your_hosts_only
Lab host you control. Hostname = $LAB_HOST. Original Cyberlium.
Opening
Scanning the apartment building subnet is everyone else's problem. YOUR lab host keeps defense where it belongs.
RoE named the host. This lesson names the asset boundary. A defensive lab belongs on a VM or workstation you own — isolated from roommates, classmates, and café patrons. $LAB_HOST is the name of that machine — not the neighbor's printer, not the airport kiosk. You verify you are logged into $LAB_HOST before any hardening or logging command. You do NOT sweep dorm subnets for 'baseline practice,' do NOT change café router settings, do NOT pivot through a classmate's RDP session. Next: RoE Lab.
1. Your host means you control the console
A lab host can be a Hyper-V VM, a VirtualBox guest, or your personal PC in an isolated VLAN — as long as YOU set the hostname to $LAB_HOST and strangers do not depend on it for production work. Document OS version and who may log in.
If you cannot reach $LAB_HOST, fix the lab topology — do not 'fix' it by hardening someone else's machine.
Command guide
Try these commands — Your host means you control the console
═══ TOOLS & WEBSITES ═══ Browse / read these (authorized learning only — stay in YOUR lab / program scope)
CIS Controls — https://www.cisecurity.org/controls MITRE D3FEND — https://d3fend.mitre.org/
═══ INSTALL ═══
Linux (Debian/Ubuntu): Built-in (iproute2)
macOS: Use: netstat
Windows: Use: netstat
═══ LINUX / macOS ═══
Command — copy this
uname -a ss -tulpn 2>/dev/null | grep -E 'LISTEN|State' | head -15 || ss -tuln | head -10
═══ WINDOWS ═══
Command — copy this
Get-ComputerInfo | Select-Object WindowsProductName, OsBuildNumber
Primary tools to practice this lesson: ss, uname. Reference sites: CIS Controls (https://www.cisecurity.org/controls); MITRE D3FEND (https://d3fend.mitre.org/). Run every command in the box — install first, then the usage lines — only on YOUR lab / program scope.
2. Disposable lab, real consequences elsewhere
Snapshot or reset the lab VM between exercises. A lab host is cattle: revert, reapply baseline, continue literacy.
Hardening or logging changes on employer production, school servers, or café gateways is out of scope forever in Cyberlium defensive modules.
3. Defender mirror
Blue teams inventory owned assets the same way: know your hostnames, alert on unknown agents, never trust 'helpful' scans from strangers. Your lab is a miniature of that discipline.
Ship one line: host=$LAB_HOST, scope=owned only, never=dorm/café/classmate gear.
4. What you ship: lab host boundary rule
Document $LAB_HOST you control. Refuse stranger subnet scans. No café router changes. chmod 600 note.
5. What you record before the next lesson
Date. OS/hostname. $LAB_HOST login proof. NEVER dorm sweeps, café gateways, classmate hosts. File t16-m01-l03-your-hosts-only.txt chmod 600.
6. Wrong vs right: stranger hosts vs YOUR lab hosts
Worked failure — same MSF word, opposite target. Right never needs a café Wi-Fi or classmate laptop.
Wrong
nmap every device on the apartment subnet 'for inventory.' Change the library Wi-Fi router password 'to secure it.'
Right
Write lab host rule and $LAB_HOST. Next: RoE Lab.
Mission: prove lab host isolation before commands
1) Document your lab OS and hostname ($LAB_HOST). 2) Record how you verify you are on the right machine before changes. 3) Login test to $LAB_HOST only — not neighbor devices. Never sweep stranger subnets.
Stuck? Ask Cyberlium AI Mentor
If $LAB_HOST is unreachable, ask Mentor about VM setup — not how to scan the dorm.
Knowledge Check
APPLY: Best target host for defensive labs in this course:
Multiple choice
Knowledge Check
APPLY: True or False: Subnet sweeps on dorm LANs are acceptable defensive prep when bored.
True or False
Knowledge Check
APPLY: $LAB_HOST in Cyberlium means:
Multiple choice