CHALLENGE INFORMATION

Platform: TryHackMe
Path: Pre Security
Module: Network Fundamentals
Room: Extending Your Network
Description: Learn about some of the technologies used to extend networks out onto the Internet and the motivations for this.

Introduction to Port Forwarding

This section covers the mechanics of port forwarding and its importance in network communications.

Question 1: What is the name of the device that is used to configure port forwarding?

Router

Firewalls 101

This section explains the differences between stateful and stateless firewalls.

Question 1: What layers of the OSI model do firewalls operate at?

Layer 3, Layer 4

Question 2: What category of firewall inspects the entire connection?

Stateful

Question 3: What category of firewall inspects individual packets?

Stateless

Practical - Firewall

The flag appears after we successfully configure the firewall on the attached static site. Our goal is to prevent a device from overloading by adding the appropriate firewall rule to the router in the middle.

Figure 1: Firewall simulation

Figure 1: Firewall simulation

We configure the router to DROP all packets accessing our web server (port 80) from the attacker’s machine (IP: 203.0.110.1).

Figure 2: Blocking malicious traffic

Figure 2: Blocking malicious traffic

Figure 3: Redacted flag

Figure 3: Redacted flag

Question 1: What is the flag?

<redacted-flag>

VPN Basics

This section introduces VPN technology, its advantages, and its various underlying technologies.

Question 1: What VPN technology only encrypts and provides the authentication of data?

PPP

Question 2: What VPN technology uses the IP framework?

IPSec

LAN Networking Devices

This section introduces LAN networking devices, including routers and switches.

Question 1: What is the verb for the action that a router does?

Routing

Question 2: What are the two different layers of switches? Separate these with a comma (i.e., LayerX, LayerY).

Layer 2, Layer 3

Practical - Network Simulator

The network simulator attached to this task breaks down the communication between two points and displays it graphically. We recommend experimenting with the simulator to better understand how communication occurs between network devices.

Figure 4: Network simulator

Figure 4: Network simulator

We send a TCP packet from computer1 to computer3 using the switches and the router along the path.

Figure 5: Simulate network traffic from C1 to C3

Figure 5: Simulate network traffic from C1 to C3

After the packet is received on computer3, a pop-up window displays the flag.

Figure 6: Redacted flag

Figure 6: Redacted flag

Below is the network log generated after sending a single TCP packet from computer1 to computer3.

StepConnection TypeNetwork Log
1HANDSHAKEStarting TCP/IP handshake between computer1 and computer3.
2HANDSHAKESending SYN packet from computer1 to computer3.
3ROUTINGcomputer1 reports that computer3 is not on the local network; sending to gateway: router.
4ARP REQUESTWho has router? Tell computer1.
5ARP RESPONSEHey computer1, I am router.
6ARP REQUESTWho has computer3? Tell router.
7ARP RESPONSEHey router, I am computer3.
8HANDSHAKEcomputer3 received SYN packet from computer1; sending SYN/ACK packet to computer1.
9HANDSHAKEcomputer1 received SYN/ACK packet from computer3; sending ACK packet to computer3.
10HANDSHAKEcomputer3 received ACK packet from computer1; handshake complete.
11TCPSending TCP packet from computer1 to computer3.
12TCPcomputer3 received TCP packet from computer1; sending ACK packet to computer1.
Table 1: Network log for sending a single TCP packet

This concludes the room and marks the completion of the Network Fundamentals module.

Question 1: What is the flag from the network simulator?

<redacted-flag>

Question 2: How many HANDSHAKE entries are there in the Network Log?

5