Lessons
Shodan Query Syntax and Filters
Lesson
Shodan is a powerful tool for searching devices connected to the internet - this includes the Internet of Things as well as traditional web facing systems like servers and routers.
ViewWhat is Graph Query Language (GQL)?
Lesson
Graph Query Language is a standardized syntax for managing, querying and manipulating property graphs.
ViewWAN Technologies - HDLC, PPP, Frame Relay and Ethernet
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Wide Area Networks may use one of several layer 2 technologies to encapsulate data as it cross a service providers network between a customer’s sites.
ViewTypes of Memory in Computer Architecture
Lesson
There are different types of memory available for storing data in a computer. Learn about what they are and what they are used for.
ViewWhat is a LAN?
Lesson
Learn about devices found on local-area networks and how they are connected.
ViewHow does IPv4 work?
Lesson
IPv4 has been at the heart of the TCP/IP stack since it's inception. It is slowly being replaced by IPv6.
ViewHow to use the man pages on Linux
Lesson
Getting help on Linux with the 'man pages' and where else to look.
ViewCDP and LLDP
Lesson
CDP and LLDP are similar layer two protocols for discovering information about neighboring devices.
ViewTelnet vs SSH
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Telnet and SSH are both protocols used for interacting with remote devices. Learn about the differences and the details.
ViewThe OSI 7 Layer Reference Model
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A conceptual network model which is often used as a reference but not implemented practically.
ViewRegex Subexpressions
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Subexpressions let us split a regular expression up into smaller groups which we can use for many things!
ViewStream Ciphers
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Stream ciphers are encryption algorithms which encrypt data one bit at a time.
ViewNetwork Proxies: The Different Types Explained
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Network proxies are seen in many networks and used by enterprises, service providers and individuals. Three of the primary uses for proxies are forward proxies (seen in enterprise networks), reverse proxies (which deliver web services) and privacy/anonymisation focused proxies.
ViewWhat are Regular Expressions?
Lesson
Regular expressions are patterns specified with a defined syntax which are used to search text for specific sequences of characters with many practical applications.
ViewIntroduction to IPv4 Routing
Lesson
IP routing is at the heart of the internet. It enables us to get packets from A to B across the globe.
ViewA Beginner's Guide to Binary
Lesson
Binary is just another way of counting. Instead of using base-10 (decimal), we use base-2 where each place value is a bit.
ViewNetwork Sockets and Ports
Lesson
Network sockets are software structures that represent the endpoints of a network connection. A pair of sockets fully specify a network connection, and these connections enable communication in both directions. There are three main types of network socket: datagram, stream and raw.
ViewSummary of the TCP/IP Model
Lesson
An overview of TCP/IP, or the Internet Protocol Suite, which underpins all modern computer networks.
ViewSame layer and adjacent layer interactions
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Learn about interactions at the same layer and between adjacent layers, including encapsulation and protocol data units (PDUs).
ViewEthernet at the Data-Link Layer
Lesson
At the data-link layer, Ethernet provides an interface between the physical layer and the higher network layers. It also specifies MAC address formats.
ViewLinux directory commands for beginners
Lesson
All the basics you need to learn for moving around the filesystem on the command line.
ViewBasic Regex Character Matching
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Learn how to match standard character classes with regular expressions.
ViewTCP: The Transmission Control Protocol
Lesson
TCP is a connection-oriented protocol used at the transport layer to support protocols such as HTTP.
ViewPing and ICMP
Lesson
Ping is a useful tool for checking network connectivity using the Internet Control Message Protocol (ICMP).
ViewDNS: The Domain Name System
Lesson
DNS is used to resolve friendly names (e.g. www.example.com) to IP addresses (e.g. 1.2.3.4), making it vital to our use of the internet.
ViewWhat is a WAN?
Lesson
Wide area networks enable data to be transferred across large geographic distances.
ViewNetcat Field Guide
Lesson
Netcat (nc) is a simple but versatile utility for TCP and UDP communication.
ViewARP: The Address Resolution Protocol
Lesson
ARP helps us match IP addresses to hardware (MAC) addresses.
ViewFirewalls in Computer Networking
Lesson
Firewalls play an important part in protecting modern computer networks.
ViewVirtual LANs (VLANs)
Lesson
VLANs are used in modern computer networks to support logically separate LANs on a single device.
ViewVLSM Subnetting in Networks
Lesson
VLSM helps make more efficient use of available IP address space.
ViewWhat do network switches do?
Lesson
Learn what network switches do in a TCP/IP network and how they work.
ViewHow does HTTP work?
Lesson
HTTP is used by web browsers and many other applications to retrieve websites and much more.
ViewRIP and RIPv2, The Routing Information Protocol
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RIP was one of the first routing protocols to be implemented. RIPv2 later added a number of improvements.
ViewCustom Sets in Regular Expressions
Lesson
Learn to define your own sets of characters to be matched with a regular expression.
ViewHashes and Computer Security
Lesson
A cryptographic hash is a one way function for which it is very difficult to get back the input when given just the output.
ViewAccess Control Lists for Beginners
Lesson
Access control lists (ACLs) provide a simple but effective layer of security in modern networks.
ViewThe Complete Guide to IPv4 Subnetting
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Learn how to design subnets and calculate the number of hosts on each.
ViewMatching a Certain Number of Repetitions with Regex
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Use regular expressions to match on a certain number (or range) of repetions of a certain character or class of characters.
ViewCollision and Broadcast Domains
Lesson
Collision and broadcast domains are important properties of an Ethernet network.
ViewRouting Between VLANs
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To let devices on one VLAN talk to the devices on another, we need to be able to route between them.
ViewEthernet at the Physical Layer
Lesson
Ethernet sits at the link layer in TCP/IP but what does it define about the OSI physical layer?
ViewHow does traceroute work?
Lesson
The traceroute command is useful tool installed on hosts and network devices for troubleshooting networking issues by tracing the route of a packet across a network.
ViewNAT: Network Address Translation
Lesson
NAT is the mapping of one address to another. It is a useful tool for conserving IP address space.
ViewRegex Anchors
Lesson
We can specify where we want to match with a regular expression using word and string boundaries.
ViewUsing tcpdump: Options, Filters and Examples
Lesson
'tcpdump' is a command-line tool available for UNIX based systems (including macOS and Linux) that captures network traffic and displays it on screen or saves it to a file. It is a simple but powerful tool for troubleshooting network problems, understanding protocols, investigating suspicious network activity, and much more.
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