Just Inherited A Network No Documentation The Admin Password Is Password123
Just Inherited A Network No Documentation The Admin Password Is Password123
1. Introduction
You walk into your first day as the sole IT administrator for a 150-person company. The server room is an unmarked closet filled with tangled cables. The previous admin vanished without leaving diagrams, passwords, or documentation. Your first breakthrough comes when you guess the domain admin password is “Password123” – and it works. This terrifying scenario is more common than most organizations admit.
In enterprise networks and homelab environments alike, undocumented infrastructure creates massive security risks and operational inefficiencies. According to Cybersecurity Ventures, 80% of network breaches stem from weak or reused passwords. Meanwhile, Gartner estimates that IT teams waste 30% of their time troubleshooting due to poor documentation.
This comprehensive guide will walk you through:
- Emergency security remediation for compromised credentials
- Network discovery techniques without documentation
- Automated documentation tools for infrastructure
- Password management best practices
- Long-term network hardening strategies
We’ll focus on practical, vendor-agnostic solutions using open-source tools that scale from homelabs to enterprise environments. You’ll learn how to transform a chaotic network into a documented, secure infrastructure using DevOps principles and infrastructure-as-code methodologies.
2. Understanding Network Documentation and Security
The Documentation Crisis
Network documentation encompasses:
- Physical topology: Device locations, cabling, power
- Logical topology: VLANs, subnets, routing
- Asset inventory: Hardware/software configurations
- Security baseline: Firewall rules, access controls
- Operational procedures: Backup schedules, maintenance
Without documentation, organizations face:
- Security vulnerabilities (like default credentials)
- Extended downtime during outages
- Compliance violations (HIPAA, PCI-DSS, GDPR)
- Knowledge silos when staff depart
Password Security Fundamentals
The “Password123” scenario violates multiple security principles:
- Password complexity: Minimum 12 characters with mixed character sets
- Password rotation: 90-day expiry for privileged accounts
- Credential segregation: Different passwords per device/service
- Multi-factor authentication: Required for administrative access
Network Discovery Approaches
When documentation is missing, use these methods:
| Method | Tools | Use Case |
|---|---|---|
| Passive discovery | Wireshark, tcpdump | Stealthy observation |
| Active scanning | Nmap, SNMP walk | Fast inventory |
| Configuration parsing | Oxidized, RANCID | Device config backup |
| API-based | NetBox, phpIPAM | IPAM integration |
3. Prerequisites
Emergency Response Toolkit
Before making network changes, assemble these tools:
- Bootable USB drive with:
- Grml Linux (for network analysis)
- Hiren’s BootCD PE (Windows recovery)
- Portable console cable (USB-to-RS232 with Cisco/HP adapters)
- Network tap or SPAN port configuration access
Software Requirements
- Network scanner:
nmap 7.92+ - SNMP tools:
snmpwalk 5.9+ - Configuration management:
Ansible 4.10+ - Documentation platform:
NetBox 3.5+
Security Precautions
- Create an isolated jump host for scanning
- Document all changes before implementation
- Notify stakeholders of potential service interruptions
- Verify backups before modifying devices
4. Emergency Network Triage
Step 1: Contain Credential Exposure
Immediately change compromised passwords using offline hash modification for domain controllers:
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# On Windows Domain Controller (elevated CMD):
ntdsutil "ac i ntds" "ifm" "create full C:\temp\ndtsbackup" q q
# Extract hashes with secretsdump.py (Impacket):
python3 secretsdump.py -system SYSTEM -ntds ntds.dit LOCAL -outputfile domain_hashes
# Identify admin accounts:
grep -a 'Administrator' domain_hashes.ntds
Rotate all passwords matching these hashes. For network devices, use Ansible emergency playbook:
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---
- name: Emergency password rotation
hosts: network_devices
gather_facts: no
vars:
new_password: ""
tasks:
- name: Change enable password on Cisco devices
cisco.ios.ios_config:
commands:
- enable secret ""
save_when: always
Step 2: Network Discovery
Perform Layer 2 discovery with CDP/LLDP:
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# Capture neighbor data from Cisco switches:
ansible switches -m cisco.ios.ios_command -a "commands='show cdp neighbor detail'" -o
# Parse LLDP data on Linux:
sudo lldpcli show neighbors
Conduct full IP sweep with Nmap:
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nmap -sn 192.168.0.0/24 -oN live_hosts.txt
nmap -sV -sC -p- -iL live_hosts.txt -oA full_scan --min-rate 1000
Step 3: Document Findings
Import results into NetBox using Python script:
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import requests
from netbox import NetBox
nb = NetBox(host='netbox.example.com', api_token='API_TOKEN')
with open('full_scan.xml') as scan_file:
for host in parse_nmap(scan_file):
nb.dcim.devices.create(
name=host['hostname'],
device_type=identify_model(host['os']),
site=find_site(host['ip']),
primary_ip4=host['ip']
)
5. Network Hardening Framework
Configuration Standards
Implement device hardening templates:
{# ios_hardening.j2 #}
no ip http server
no ip http secure-server
service password-encryption
enable secret
access-list 22 permit
line vty 0 4
access-class 22 in
transport input ssh
Apply via Ansible:
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- name: Harden Cisco devices
cisco.ios.ios_config:
src: "templates/ios_hardening.j2"
Password Management
Deploy Hashicorp Vault with SSH OTP:
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# Configure Vault SSH secrets engine:
vault secrets enable ssh
vault write ssh/roles/otp_key_role key_type=otp default_user=admin cidr_list=10.0.0.0/8
# Generate OTP for network device access:
vault write ssh/creds/otp_key_role ip=192.168.1.1 username=admin
Automated Documentation
NetBox data model for network documentation:
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# netbox_data.yml
sites:
- name: Main Data Center
slug: main-dc
physical_address: 123 Example St
devices:
- name: core-switch-01
device_type: Cisco C9300
role: core-switch
site: main-dc
interfaces:
- name: GigabitEthernet1/0/1
type: 1000base-t
description: Uplink to firewall
6. Operational Maintenance
Daily Tasks
- Review authentication logs for brute-force attempts:
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# Linux servers:
journalctl -u sshd | grep 'Failed password'
# Cisco devices:
show logging | include AAA.*Failed
- Verify backup integrity:
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# Check RANCID config diffs:
git -C /var/lib/rancid/ diff @{yesterday}
Weekly Tasks
- Audit administrative access:
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# Check domain admin group membership:
Get-ADGroupMember 'Domain Admins' | Export-CSV domain_admins.csv
- Validate firewall rule compliance:
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# Ansible playbook for firewall audit:
ansible-playbook audit_firewalls.yml --tags compliance
7. Troubleshooting Common Issues
Problem: Intermittent Connectivity
Diagnosis:
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mtr -4zwc 100 8.8.8.8 # IPv4 path analysis
mtr -6zwc 100 2001:4860:4860::8888 # IPv6 path analysis
Solution: Check for asymmetric routing with flow logs:
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tshark -i eth0 -Y "tcp.analysis.retransmission" -w retransmits.pcap
Problem: Device Configuration Drift
Diagnosis:
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rancid-run -diff # Compare running vs archived configs
Solution: Enforce configuration compliance with Ansible:
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- name: Remediate configuration drift
cisco.ios.ios_config:
backup: yes
replace: block
src: "templates/.cfg"
8. Conclusion
Inheriting an undocumented network with compromised credentials requires methodical triage: contain immediate threats, discover actual infrastructure, implement secure baselines, and establish automated documentation. The tools and workflows demonstrated here turn chaos into operational resilience.
For continued learning:
- Nmap Network Scanning (Official Guide)
- Network Programmability and Automation (O’Reilly)
- CIS Network Device Benchmarks
Remember: Documentation isn’t about creating pretty diagrams - it’s about building institutional memory that survives staff turnover. In your next role interview, ask “What’s your process for network documentation?” The answer will reveal much about their operational maturity.