Key Components of SSH 🔑

• SSH Client: This is the software on your computer that you use to start the secret tunnel.
• SSH Server: This is the software running on the remote computer that waits for your tunnel requests and lets you in.

The Tools Explained for Beginners 🧰

• 1. Termius (Windows, Mac, Android)
  • What it is:Termius is like a friendly, modern dashboard for managing all your secret tunnels (SSH connections). It has a graphical user interface (GUI), meaning you click buttons and type into boxes, which is usually easier for beginners.

  How to use it (Simplified)

  • 1.Install it: Download and install Termius on your computer or phone.
  • 2.Add a New Host: In Termius, you'll see a button or option to "Add New Host" or "New Connection.
  • 3.Enter Server Details: Type in the address of the remote computer (like a website address, e.g., my-server.com or an IP address like 192.168.1.100) and the username you want to log in as (e.g., admin or myuser)
  • 4.Connect! Click "Connect" or "Save & Connect." Termius will then prompt you for a password (if you use one) or use a "key" (more on that later).
  • 5.You're In: Once connected, you'll see a black screen where you can type commands to control the remote computer.

Here's a breakdown of its key features and options 🔒

1. Basic SSH Connection & Options
At its core, ssh connects you to a remote machine.

How to connect

ssh username@hostname_or_IP

• username: Your user account on the remote machine.
• hostname_or_IP: The domain name (e.g., example.com) or IP address (e.g., 192.168.1.100) of the remote machine.
Example:ssh user@my-server.com
• -p port(Specify Port):If the SSH server on the remote machine is not listening on the default port (22), you can specify it.
Example:ssh -p 2222 user@my-server.com (Connects to port 2222)
• -l login_name(Specify Username):An alternative way to specify the username.
Example:ssh -l user my-server.com (Same as ssh user@my-server.com)
• -v(Verbose Mode): Extremely useful for troubleshooting! It makes ssh print out detailed messages about what it's doing during the connection process. You can use -vv or -vvv for even more detail.
Example:ssh -v user@my-server.com
• -f (Background before command): Makes ssh go to the background before running a command on the remote server. This is useful if you want to start a remote process but don't want to keep your local terminal open for it. Often used with -n.
Example:ssh -f myuser@remote.com "firefox &" (Starts Firefox on the remote machine and sends SSH to the background)
• -n(No standard input):Prevents ssh from reading from standard input. This is important when ssh is run in the background, so it doesn't wait for your input.
2. Authentication Methods
SSH uses various ways to verify your identity to the server. The most common and secure methods for beginners are Public Key Authentication and Password Authentication.
• Password Authentication:The simplest method. You provide your password for the remote user. All communication, including the password, is encrypted.
• Public Key Authentication (Recommended):This is more secure and convenient for regular use.
• You generate a pair of keys:a public key and a private key.
• The public key is stored on the remote server (in ~/.ssh/authorized_keys in your home directory).
• The private keystays securely on your local computer (e.g., ~/.ssh/id_rsa).
• When you connect,ssh uses your private key to prove your identity without sending your password over the network.
• How to generate keys:ssh-keygen (just type this in your terminal and follow the prompts).
• How to use a specific key:ssh -i ~/.ssh/my_custom_key user@my-server.com
• Authentication Agent(ssh-agent & -A):
• ssh-agent is a program that holds your private keys in memory so you don't have to type your passphrase every time you use them.
• -A(Enable Agent Forwarding):This allows you to use your local ssh-agent keys when connecting from the remote server to another server. Use with caution, as it can be a security risk if the remote server is compromised.
• Example:ssh -A user@first-server (Now, from first-server, you can ssh to second-server using your local keys without re-entering passphrases).
3. Checking Server Identity (known_hosts)
When you connect to an SSH server for the first time, ssh will show you its "fingerprint" and ask if you want to accept it.
• known_hosts: Stores server "fingerprints" to verify you're connecting to the right machine.
• Security:If a fingerprint changes, ssh warns you – a sign of a potential attack.
4. Special Session Controls (Escape Characters)
While connected, type ~ (tilde) at the beginning of a new line, followed by:
• ~.:Disconnect immediately.
• ~?:Show all escape options.
5. Secure Data Tunnels (Port Forwarding)
SSH can "tunnel" network traffic securely.
• -L local_port:remote_host:remote_port(Local Forwarding):Access a service on the remote network through a local port on your machine.
• Example: ssh -L 8080:localhost:80 web.example.com (Access web.example.com's port 80 via your localhost:8080).
• -D local_port(Dynamic Forwarding / SOCKS Proxy): Turn your SSH client into a SOCKS proxy. All your selected application traffic goes through the SSH tunnel.
• Example: ssh -D 8080 user@proxy-server.com (Browse securely via proxy-server.com).
6. Running Graphical Apps Remotely (X11 Forwarding)
X11 is the system used by many Unix-like operating systems (like Linux) for graphical user interfaces (GUIs).
• -X: Show remote graphical applications on your local desktop.
• Example: ssh -X user@remote-gui "firefox" (Run Firefox on the remote server, see it on your screen).
• -Y: A less secure version of -X, use only if you fully trust the server.
7. Important SSH Files
Look in your ~/.ssh/ folder:
• -~/.ssh/config: Your personal settings for SSH (e.g., shorthand for servers).
• ~/.ssh/known_hosts: Saved server fingerprints.
• ~/.ssh/authorized_keys (on server): Where your public key goes so the server knows you're allowed to log in.
• ~/.ssh/id_rsa (etc.): Your private key (keep secret!).

We recommend reading more from ssh(1) - Linux man page




What is SQL?


Structured Query Language (SQL) is a programming language for storing and processing data in relational databases. Relational databases store data in tabular form with rows and columns representing different data categories and relationships between data values. SQL commands can be used to store, update, delete, search, and retrieve data from a database. Additionally, SQL can be used to maintain and optimize database performance.

Key Components of SQL 🔑

• SDatabase:A structured collection of data, like a digital filing cabinet.
• Table:Where data is actually stored within a database, organized into rows and columns (like a spreadsheet).
• Row (Record): A single entry or record in a table (e.g., one customer's details).
• Column (Field): A specific category of data in a table (e.g., "FirstName", "Email").
• Primary Key: A column (or set of columns) that uniquely identifies each row in a table.
• Foreign Key:A column that links rows between two tables, ensuring data integrity.

The Tools Explained for Beginners 🧰

To write and run SQL, you typically use a Database Management System (DBMS) or a SQL Client.
• 1. Online SQL Editors (No Installation Required!)
  • What it is: Web-based tools that let you write and execute SQL queries directly in your browser, often with sample data. Perfect for absolute beginners to practice without setting up a local database.

  How to use it (Simplified)

  • 1.Visit Website: Go to a site like W3Schools SQL Editor or SQLBolt.
  • 2.Type Query: Write your SQL command in the provided editor area.
  • 3.Run: Click a "Run" or "Execute" button.
  • 4.See Results: The results of your query (or an error message) will appear.
• Why it's good for beginners: Instant practice, zero setup, great for understanding syntax.
• 2. Desktop Database Tools (e.g., DBeaver, MySQL Workbench, pgAdmin)
  • What it is:Dedicated software installed on your computer to connect to, manage, and query various types of databases (MySQL, PostgreSQL, SQL Server, SQLite, etc.). They offer powerful features and a graphical interface.

  How to use it (Simplified)

  • Install: Download and install the tool (e.g., DBeaver).
  • 2.Connect to Database: Set up a new connection by providing database server details (host, port, username, password). You might first need to install a local database server (e.g., SQLite, MySQL).
  • 3.Open Query Editor: Find the SQL editor window within the tool.
  • 4.Write & Run: Type your SQL queries and execute them.
  • 5.View & Manage: See query results, browse table structures, and manage database objects.

Key Features and Options 🔓

SQL is primarily about CRUD operations (Create, Read, Update, Delete) on data
• SELECT: Get data. SELECT * FROM Customers;
• INSERT INTO: Add data. INSERT INTO Products VALUES ('Monitor');
• UPDATE: Change data. UPDATE Users SET Email = 'new@example.com';
• DELETE FROM: Remove data (use with caution!). DELETE FROM Orders WHERE ID = 1;
• WHERE Clause:Filters data (e.g., WHERE Age > 30).
• JOIN:Combines data from multiple tables.

SQL Injection & Prevention 🛡️

A critical security concern in SQL is SQL Injection.
• What it is:A web security vulnerability where attackers insert malicious SQL code into input fields (e.g., login forms, search bars) to trick the database into executing unintended commands. This can lead to data theft, modification, or even database control.
• Prevention (Most Important for Developers):
• Prepared Statements / Parameterized Queries: This is the primary and most effective defense. It separates the SQL code from user-provided data, so the database never mistakes user input for commands.
• Input Validation: Strictly check and sanitize all user input, allowing only expected formats and content.
• Least Privilege: Configure database user accounts with only the minimum necessary permissions.

We recommend reading more from w3schools - SQL

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Use virustotal

• virustotal.(virustotal.com)