Network 101

Network 101

Purpose

Configure and test common network services (HTTP, HTTPS, SNMP, SMB) for penetration testing lab environments. Enable hands-on practice with service enumeration, log analysis, and security testing against properly configured target systems.

Inputs/Prerequisites

• Windows Server or Linux system for hosting services
• Kali Linux or similar for testing
• Administrative access to target system
• Basic networking knowledge (IP addressing, ports)
• Firewall access for port configuration

Outputs/Deliverables

• Configured HTTP/HTTPS web server
• SNMP service with accessible communities
• SMB file shares with various permission levels
• Captured logs for analysis
• Documented enumeration results

Core Workflow

1. Configure HTTP Server (Port 80)

Set up a basic HTTP web server for testing:

Windows IIS Setup:

1. Open IIS Manager (Internet Information Services)
2. Right-click Sites → Add Website
3. Configure site name and physical path
4. Bind to IP address and port 80

Linux Apache Setup:

# Install Apache
sudo apt update && sudo apt install apache2

# Start service
sudo systemctl start apache2
sudo systemctl enable apache2

# Create test page
echo "<html><body><h1>Test Page</h1></body></html>" | sudo tee /var/www/html/index.html

# Verify service
curl http://localhost

Configure Firewall for HTTP:

# Linux (UFW)
sudo ufw allow 80/tcp

# Windows PowerShell
New-NetFirewallRule -DisplayName "HTTP" -Direction Inbound -Protocol TCP -LocalPort 80 -Action Allow

2. Configure HTTPS Server (Port 443)

Set up secure HTTPS with SSL/TLS:

Generate Self-Signed Certificate:

# Linux - Generate certificate
sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 \
  -keyout /etc/ssl/private/apache-selfsigned.key \
  -out /etc/ssl/certs/apache-selfsigned.crt

# Enable SSL module
sudo a2enmod ssl
sudo systemctl restart apache2

Configure Apache for HTTPS:

# Edit SSL virtual host
sudo nano /etc/apache2/sites-available/default-ssl.conf

# Enable site
sudo a2ensite default-ssl
sudo systemctl reload apache2

Verify HTTPS Setup:

# Check port 443 is open
nmap -p 443 192.168.1.1

# Test SSL connection
openssl s_client -connect 192.168.1.1:443

# Check certificate
curl -kv https://192.168.1.1

3. Configure SNMP Service (Port 161)

Set up SNMP for enumeration practice:

Linux SNMP Setup:

# Install SNMP daemon
sudo apt install snmpd snmp

# Configure community strings
sudo nano /etc/snmp/snmpd.conf

# Add these lines:
# rocommunity public
# rwcommunity private

# Restart service
sudo systemctl restart snmpd

Windows SNMP Setup:

1. Open Server Manager → Add Features
2. Select SNMP Service
3. Configure community strings in Services → SNMP Service → Properties

SNMP Enumeration Commands:

# Basic SNMP walk
snmpwalk -c public -v1 192.168.1.1

# Enumerate system info
snmpwalk -c public -v1 192.168.1.1 1.3.6.1.2.1.1

# Get running processes
snmpwalk -c public -v1 192.168.1.1 1.3.6.1.2.1.25.4.2.1.2

# SNMP check tool
snmp-check 192.168.1.1 -c public

# Brute force community strings
onesixtyone -c /usr/share/seclists/Discovery/SNMP/common-snmp-community-strings.txt 192.168.1.1

4. Configure SMB Service (Port 445)

Set up SMB file shares for enumeration:

Windows SMB Share:

1. Create folder to share
2. Right-click → Properties → Sharing → Advanced Sharing
3. Enable sharing and set permissions
4. Configure NTFS permissions

Linux Samba Setup:

# Install Samba
sudo apt install samba

# Create share directory
sudo mkdir -p /srv/samba/share
sudo chmod 777 /srv/samba/share

# Configure Samba
sudo nano /etc/samba/smb.conf

# Add share:
# [public]
#    path = /srv/samba/share
#    browsable = yes
#    guest ok = yes
#    read only = no

# Restart service
sudo systemctl restart smbd

SMB Enumeration Commands:

# List shares anonymously
smbclient -L //192.168.1.1 -N

# Connect to share
smbclient //192.168.1.1/share -N

# Enumerate with smbmap
smbmap -H 192.168.1.1

# Full enumeration
enum4linux -a 192.168.1.1

# Check for vulnerabilities
nmap --script smb-vuln* 192.168.1.1

5. Analyze Service Logs

Review logs for security analysis:

HTTP/HTTPS Logs:

# Apache access log
sudo tail -f /var/log/apache2/access.log

# Apache error log
sudo tail -f /var/log/apache2/error.log

# Windows IIS logs
# Location: C:\inetpub\logs\LogFiles\W3SVC1\

Parse Log for Credentials:

# Search for POST requests
grep "POST" /var/log/apache2/access.log

# Extract user agents
awk '{print $12}' /var/log/apache2/access.log | sort | uniq -c

Quick Reference

Essential Ports

| Service | Port | Protocol | |---------|------|----------| | HTTP | 80 | TCP | | HTTPS | 443 | TCP | | SNMP | 161 | UDP | | SMB | 445 | TCP | | NetBIOS | 137-139 | TCP/UDP |

Service Verification Commands

# Check HTTP
curl -I http://target

# Check HTTPS
curl -kI https://target

# Check SNMP
snmpwalk -c public -v1 target

# Check SMB
smbclient -L //target -N

Common Enumeration Tools

| Tool | Purpose | |------|---------| | nmap | Port scanning and scripts | | nikto | Web vulnerability scanning | | snmpwalk | SNMP enumeration | | enum4linux | SMB/NetBIOS enumeration | | smbclient | SMB connection | | gobuster | Directory brute forcing |

Constraints

• Self-signed certificates trigger browser warnings
• SNMP v1/v2c communities transmit in cleartext
• Anonymous SMB access is often disabled by default
• Firewall rules must allow inbound connections
• Lab environments should be isolated from production

Examples

Example 1: Complete HTTP Lab Setup

# Install and configure
sudo apt install apache2
sudo systemctl start apache2

# Create login page
cat << 'EOF' | sudo tee /var/www/html/login.html
<html>
<body>
<form method="POST" action="login.php">
Username: <input type="text" name="user"><br>
Password: <input type="password" name="pass"><br>
<input type="submit" value="Login">
</form>
</body>
</html>
EOF

# Allow through firewall
sudo ufw allow 80/tcp

Example 2: SNMP Testing Setup

# Quick SNMP configuration
sudo apt install snmpd
echo "rocommunity public" | sudo tee -a /etc/snmp/snmpd.conf
sudo systemctl restart snmpd

# Test enumeration
snmpwalk -c public -v1 localhost

Example 3: SMB Anonymous Access

# Configure anonymous share
sudo apt install samba
sudo mkdir /srv/samba/anonymous
sudo chmod 777 /srv/samba/anonymous

# Test access
smbclient //localhost/anonymous -N

Troubleshooting

| Issue | Solution | |-------|----------| | Port not accessible | Check firewall rules (ufw, iptables, Windows Firewall) | | Service not starting | Check logs with journalctl -u service-name | | SNMP timeout | Verify UDP 161 is open, check community string | | SMB access denied | Verify share permissions and user credentials | | HTTPS certificate error | Accept self-signed cert or add to trusted store | | Cannot connect remotely | Bind service to 0.0.0.0 instead of localhost |