# To Scan a Network

Usually on certifications labs or execuing a pentestration test on a client we have define in our scope a sub net with specified range of IPs.

Before start scanning the network I usually execute some commands on my machine to verify what interface is associated with the VPN to verify my IP and verify my ARP table.

### What to expect?

Networks can filter types of traffic or traffic to specific port numbers. Pay attention if you trying to get a reverse shell on a random port number, that port could be blocked.

### What if the Network is blocking some types of traffic?

As I said networks can filter types of traffic like TCP/UDP/SCTP/ICMP or even IP, yes IP! 

UDP traffic can be block only for a specific host and allowed for other inside the same subnet. 

Or can be blocked on all subnet.

In these case we need to test the network for each host we we've found.

### Traceroute is our Friend!

Traceroute using TCP

```
sudo traceroute -T 192.168.4.5
```

Traceroute using UDP

```
sudo traceroute -U 192.168.4.5
```

#### Traceroute using ICMP

```
sudo traceroute -I 192.168.4.5
```

### Keep in Mind

### Methodology To Scan a Network

**Identify the Network Range**

Start by determining the range of IP addresses within the scope of the penetration test. This information is typically provided in the rules of engagement document.

```bash
# Example command for identifying local network interface details
ip addr show
```

**Reconnaissance**

Perform initial reconnaissance to gather as much information as possible about the target network. This may include using tools like `nmap` to discover hosts, services, and their characteristics.

```bash
# Example Nmap command to discover live hosts
nmap -sn 192.168.4.0/24
```

**Port Scanning**

After identifying active hosts, proceed to scan for open ports and running services to gather more granular intelligence.

```bash
# Example Nmap command to scan for open ports
nmap -p 1-65535 192.168.4.5
```

**Vulnerability Assessment**

Analyze the discovered services for known vulnerabilities using automated tools or manual techniques. Tools like OpenVAS or Nessus can be used for automated scans.

**Analysis and Planning**

Analyze the data collected to identify potential attack vectors. Use this information to plan your penetration test, such as what tools and exploits to use.

**Exploitation**

Attempt to exploit identified vulnerabilities to gain unauthorized access, escalate privileges, or gather sensitive data.

**Post-Exploitation**

Once access is gained, further explore the network to discover additional systems, data, and maintain persistence if within the scope.

**Reporting**

Document all discovered vulnerabilities, exploited systems, and recommended remediation strategies in a detailed report for the client.

**Cleanup**

Ensure that any modifications made to the target network during the test are reverted to leave the network in its original state.