Cyber Security Basics for Beginners

What is Networking?

According to Wikipedia, A computer network is a group of computers that use a set of common communication protocols over digital interconnections for the purpose of sharing resources located on or provided by the network nodes. The interconnections between nodes are formed from a broad spectrum of telecommunication network technologies, based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.

What is Internet?

The Internet is one giant network that consists of many, many small networks within itself. 

How to Identify devices on a Network?

In order To communicate and maintain operation, devices must be both identifying and identifiable on a network. 

So we use these in order to maintain communication between devices:

• An IP Address
• A Media Access Control (MAC) Address — think of this as being similar to a serial number.

IP Address:

• Two Versions of Addressing Scheme
  • IP version 4 – 32 bit addressing
  • IP version 6 – 128 bit addressing

IP address Classes

• CLASS A Range
  • 0.0.0.0  – 127.255.255.255
• CLASS B Range
  • 128.0.0.0 – 191.255.255.255
• CLASS C Range
  • 192.0.0.0 – 223.255.255.255
• CLASS D Range
  • 224.0.0.0 – 239.255.255.255
• CLASS E Range
  • 240.0.0.0 – 255.255.255.255

• Private IP Address
  • CLASS  A 10.0.0.0 – 10.255.255.255
  • CLASS  B 172.16.0.0 – 172.31.255.255
  • CLASS  C 192.168.0.0 – 192.168.255.255
• Public  IP Address
  • Apart from the above specified IP addresses all other IP addresses are  Public IP’s

Assigning IP address via Command Prompt Example

        Netsh interface ipv4 set address name=“Ethernet” source=static addr=10.0.0.1 mask=255.0.0.0

MAC Addresses

Devices on a network will all have a physical network interface, which is a microchip board found on the device’s motherboard.

This network interface is assigned a unique address at the factory it was built at, called a MAC (Media Access Control ) address.

The MAC address is a sixteen-character hexadecimal number (a base sixteen numbering system used in computing to represent numbers) split into two’s and separated by a colon, for example, a4:c3:f0:85:ac:2d.

The first six characters represent the company that made the network interface, and the last six is a unique number.

However, an interesting thing with MAC addresses is that they can be faked or “spoofed” in a process known as spoofing.

This spoofing occurs when a networked device pretends to identify as another using its MAC address. When this occurs, it can often break poorly implemented security designs that assume that devices talking on a network are trustworthy.

Take the following scenario: A firewall is configured to allow any communication going to and from the MAC address of the administrator. If a device were to pretend or “spoof” this MAC address, the firewall would now think that it is receiving communication from the administrator when it isn’t.

PING(ICMP)

Ping is one of the most fundamental network tools available to us.

Ping uses ICMP (Internet Control Message Protocol) packets to determine the performance of a connection between devices, for example, if the connection exists or is reliable.

The syntax to do a simple ping is ping IP address or website URL

Extending Your Network

 Introduction to Port Forwarding

Port forwarding is an essential component in connecting applications and services to the Internet. Without port forwarding, applications and services such as web servers are only available to devices within the same direct network.

In comparison, firewalls determine if traffic can travel across these ports (even if these ports are open by port forwarding).

While the standard rule for web data is port 80, a few other protocols have been allocated a standard rule. Any port that is within 0 and 1024 (1,024) is known as a common port. Let’s explore some of these other protocols below:

 Firewalls

A firewall is a device within a network responsible for determining what traffic is allowed to enter and exit. 

Layer 3, Layer 5 of the OSI model are the layers where the firewalls operate at.

VPN

A Virtual Private Network (or VPN for short) is a technology that allows devices on separate networks to communicate securely by creating a dedicated path between each other over the Internet (known as a tunnel). Devices connected within this tunnel form their own private network.

VPN technology has improved over the years. Let’s explore some existing VPN technologies below: