😱In computing, a daemon is a type of program that runs in the background, performing system tasks without direct user interaction. They are often associated with Unix and Unix-like operating systems like Linux and macOS. Daemons typically start automatically when a system boots up and manage system resources, handle network connections, or provide services for other programs.
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📚 OS Concepts — What is a Trap? What is a Trap Table? 🧵
Let’s break down one of the coolest mechanisms your OS uses to switch into "superpower mode" 🦸♂️
🔹 Trap = Software Interrupt
🛎 Happens when a user program needs to request OS services
📞 Example: read(), write(), fork() → These trigger traps
⚙️ Transfers control to the kernel via a safe & controlled mechanism
⏱️ Happens synchronously (exact instruction, not random)
🔹 Trap Table = Phonebook for the OS
🧠 It’s a table that maps trap numbers → handler functions
📍 When a trap happens, the CPU consults the table to know where to jump
💥 Example: Trap 0x80 in Linux → syscall handler
#OS #Traps #SystemCalls #Interrupts #TrapTable #KernelMode
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Let’s break down one of the coolest mechanisms your OS uses to switch into "superpower mode" 🦸♂️
🔹 Trap = Software Interrupt
🛎 Happens when a user program needs to request OS services
📞 Example: read(), write(), fork() → These trigger traps
⚙️ Transfers control to the kernel via a safe & controlled mechanism
⏱️ Happens synchronously (exact instruction, not random)
🔹 Trap Table = Phonebook for the OS
🧠 It’s a table that maps trap numbers → handler functions
📍 When a trap happens, the CPU consults the table to know where to jump
💥 Example: Trap 0x80 in Linux → syscall handler
#OS #Traps #SystemCalls #Interrupts #TrapTable #KernelMode
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❌Inline hooking is a technique where malware (or legitimate software) modifies the beginning of a function's code—usually by overwriting the first few bytes with a jump (JMP) instruction to custom (malicious) code. This allows the attacker to intercept function calls and either:
Alter inputs or outputs
Inject new behavior
Hide actions or data
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Alter inputs or outputs
Inject new behavior
Hide actions or data
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❌❌وام سامانه حمایت کلاهبرداری است
بانک مرکزی با صدور اطلاعیه ای ضمن تکذیب انتشار برخی ادعاها مبنی بر پرداخت تسهیلات بانکی از طریق سامانه هایی در فضای مجازی تاکید کرد: برنامه این بانک در خصوص تامین مالی خرد به صورت رسمی در پایگاه اطلاع رسانی این بانک اعلام می شود و هرگونه اخبار مرتبط با پرداخت تسهیلات در فضای مجازی و رسانه های غیررسمی مورد تایید این نهاد نیست.
اخیرا در فضای مجازی اخباری با محتوای «وام ۱۵۰ میلیون تومانی از طریق سامانه حمایت» در حال انتشار است که از اساس این اخبار شایعه بوده و صرفا با هدف #کلاهبرداری و جمع آوری اطلاعات اشخاص صورت می گیرد. #هشدار
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بانک مرکزی با صدور اطلاعیه ای ضمن تکذیب انتشار برخی ادعاها مبنی بر پرداخت تسهیلات بانکی از طریق سامانه هایی در فضای مجازی تاکید کرد: برنامه این بانک در خصوص تامین مالی خرد به صورت رسمی در پایگاه اطلاع رسانی این بانک اعلام می شود و هرگونه اخبار مرتبط با پرداخت تسهیلات در فضای مجازی و رسانه های غیررسمی مورد تایید این نهاد نیست.
اخیرا در فضای مجازی اخباری با محتوای «وام ۱۵۰ میلیون تومانی از طریق سامانه حمایت» در حال انتشار است که از اساس این اخبار شایعه بوده و صرفا با هدف #کلاهبرداری و جمع آوری اطلاعات اشخاص صورت می گیرد. #هشدار
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⛑Ubuntu 25.10 Switches to Rust-based Sudo!!
https://www.omgubuntu.co.uk/2025/05/ubuntu-25-10-rust-sudo-rs-change
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https://www.omgubuntu.co.uk/2025/05/ubuntu-25-10-rust-sudo-rs-change
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OMG! Ubuntu
Ubuntu 25.10 Switches to Rust-based Sudo
Ubuntu 25.10 will replace the sudo command with sudo-rs, a new Rust rewrite designed to improve memory safety and security. What does this mean for users?
🔧 What is a System Call (Syscall)?
A system call is a controlled entry point that allows user-mode applications to request services from the kernel (like reading a file, opening a network socket, etc.).
🕵️ What is Syscall Hijacking?
Syscall hijacking is when a rootkit modifies or redirects system calls to its own malicious functions, instead of letting them reach the legitimate kernel handlers.
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A system call is a controlled entry point that allows user-mode applications to request services from the kernel (like reading a file, opening a network socket, etc.).
🕵️ What is Syscall Hijacking?
Syscall hijacking is when a rootkit modifies or redirects system calls to its own malicious functions, instead of letting them reach the legitimate kernel handlers.
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🏢 2. OV – Organization Validation
Purpose: Encrypts and authenticates the organization behind the domain.
✅ Validation Level: Confirms domain ownership and verifies company details (via business registration, phone, etc.)
📄 Certificate Info: Includes organization name and location
👁 Browser Bar: Padlock only, but company name visible in cert details
💰 Cost: Moderate
🧰 Use Case: Business websites, login portals, B2B platforms
Example:
Issued to: example.com
Organization: Example Corp, US
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Purpose: Encrypts and authenticates the organization behind the domain.
✅ Validation Level: Confirms domain ownership and verifies company details (via business registration, phone, etc.)
📄 Certificate Info: Includes organization name and location
👁 Browser Bar: Padlock only, but company name visible in cert details
💰 Cost: Moderate
🧰 Use Case: Business websites, login portals, B2B platforms
Example:
Issued to: example.com
Organization: Example Corp, US
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📚 OS Concepts — What Happens When the System Runs Out of RAM? 💥🧵
Let’s break down how the OS reacts when memory is almost full! 🔍
🧠 The Problem:
Your system is running low on RAM. New apps need memory, but there’s no space left! What does the OS do?
🔹 Option 1: Swapping / Paging Out
💽 Move memory pages from RAM → disk (swap area)
🧊 Frees up RAM for urgent tasks
⚠️ Disk is much slower → system may feel sluggish ("thrashing")
📌 Think: Push books to a shelf to make space on your desk
🔹 Option 2: Killing Processes (OOM Killer / LMK)
💀 OS starts terminating processes to free memory
🧠 OOM Killer (Linux): kills least important process
📱 LMK (Android): aggressively frees memory by killing background apps
⚠️ Risk: Important work may be lost if a process is killed
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Let’s break down how the OS reacts when memory is almost full! 🔍
🧠 The Problem:
Your system is running low on RAM. New apps need memory, but there’s no space left! What does the OS do?
🔹 Option 1: Swapping / Paging Out
💽 Move memory pages from RAM → disk (swap area)
🧊 Frees up RAM for urgent tasks
⚠️ Disk is much slower → system may feel sluggish ("thrashing")
📌 Think: Push books to a shelf to make space on your desk
🔹 Option 2: Killing Processes (OOM Killer / LMK)
💀 OS starts terminating processes to free memory
🧠 OOM Killer (Linux): kills least important process
📱 LMK (Android): aggressively frees memory by killing background apps
⚠️ Risk: Important work may be lost if a process is killed
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📚 OS & Computer Architecture — Understanding Caches & TLB 🧵
Let’s break down how your system stores & accesses memory efficiently!
🔸 A. L1 Cache (Level 1 Cache)
⚡️ Ultra-fast, small-sized cache (typically 16KB–128KB)
📍 Located inside the CPU core
🧠 Stores frequently used instructions & data
⚙️ Split into L1-I (Instructions) and L1-D (Data)
⏱️ Fastest access (~1–2 CPU cycles)
🚀 Purpose: Minimize delay between CPU and memory
🔸 B. Page Cache
🗃 Part of the OS's memory management
💾 Caches data read from or written to disk
🎯 Works at the file system level (pages, not bytes)
📈 Improves I/O performance by reducing disk access
✅ Example:
When you cat file.txt, the data goes to page cache so next reads are instant (RAM-based)!
🔸 C. TLB (Translation Lookaside Buffer)
🧭 Special cache inside the CPU
🔁 Maps virtual addresses → physical addresses
📍 Speeds up memory address translation
🔄 Without TLB, each memory access requires a page table lookup
⏱️ Much faster than walking full page tables
🚨 TLB Miss = CPU has to do extra work (slow)
🔸 D. L3 Cache (Level 3 Cache)
📦 Shared cache across multiple CPU cores
🔁 Larger but slower than L1/L2 (e.g., 4MB–64MB)
📉 Latency: ~10–20 CPU cycles
🧠 Holds data that doesn't fit in L1/L2 but is still reused often
🧰 Acts as a "last chance" before going to main memory
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Let’s break down how your system stores & accesses memory efficiently!
🔸 A. L1 Cache (Level 1 Cache)
⚡️ Ultra-fast, small-sized cache (typically 16KB–128KB)
📍 Located inside the CPU core
🧠 Stores frequently used instructions & data
⚙️ Split into L1-I (Instructions) and L1-D (Data)
⏱️ Fastest access (~1–2 CPU cycles)
🚀 Purpose: Minimize delay between CPU and memory
🔸 B. Page Cache
🗃 Part of the OS's memory management
💾 Caches data read from or written to disk
🎯 Works at the file system level (pages, not bytes)
📈 Improves I/O performance by reducing disk access
✅ Example:
When you cat file.txt, the data goes to page cache so next reads are instant (RAM-based)!
🔸 C. TLB (Translation Lookaside Buffer)
🧭 Special cache inside the CPU
🔁 Maps virtual addresses → physical addresses
📍 Speeds up memory address translation
🔄 Without TLB, each memory access requires a page table lookup
⏱️ Much faster than walking full page tables
🚨 TLB Miss = CPU has to do extra work (slow)
🔸 D. L3 Cache (Level 3 Cache)
📦 Shared cache across multiple CPU cores
🔁 Larger but slower than L1/L2 (e.g., 4MB–64MB)
📉 Latency: ~10–20 CPU cycles
🧠 Holds data that doesn't fit in L1/L2 but is still reused often
🧰 Acts as a "last chance" before going to main memory
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🐞CVE is a catalog of known software flaws, with each ID representing a specific vulnerability. CWE, on the other hand, is a category system for software and hardware weaknesses that can lead to vulnerabilities.
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🥃Mitigating DDoS attacks ontheinternet ofthings using federated learning
Link
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📚 OS Concepts — Cooperative vs Preemptive Scheduling 🧵
Ever wondered how your computer decides who gets the CPU and when? Let’s break it down:
🔹 1. Cooperative Scheduling
🤝 The process gives up the CPU voluntarily
🛑 If it never gives up, no one else runs
⚠️ One buggy program = system freeze
🏗 Used in old Windows, embedded systems
🔹 2. Preemptive Scheduling (Non-Cooperative)
⏱️ OS uses a timer to interrupt running processes
🔁 CPU is forcefully switched between tasks
💪 More stable & fair
🏃 Used in Linux, Android, Windows, etc.
📌 Key Difference:
Cooperative: “I’ll tell you when I’m done”
Preemptive: “Time’s up! Next process please”
💡
#OS #Scheduling #Preemptive #Cooperative #CSBasics #InfoSecTube
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Ever wondered how your computer decides who gets the CPU and when? Let’s break it down:
🔹 1. Cooperative Scheduling
🤝 The process gives up the CPU voluntarily
🛑 If it never gives up, no one else runs
⚠️ One buggy program = system freeze
🏗 Used in old Windows, embedded systems
🔹 2. Preemptive Scheduling (Non-Cooperative)
⏱️ OS uses a timer to interrupt running processes
🔁 CPU is forcefully switched between tasks
💪 More stable & fair
🏃 Used in Linux, Android, Windows, etc.
📌 Key Difference:
Cooperative: “I’ll tell you when I’m done”
Preemptive: “Time’s up! Next process please”
💡
Modern OS = Preemptive, for fairness + safety!#OS #Scheduling #Preemptive #Cooperative #CSBasics #InfoSecTube
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🪡Internet Key Exchange (IKE) is a secure key management protocol that establishes secure, authenticated communication channels over IP networks. It's used to set up security associations (SAs) in Internet Protocol Security (IPsec) for VPN connections, ensuring both parties use common encryption and authentication methods for secure data exchange.
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🏛 3. EV – Extended Validation
Purpose: Maximum trust; strictest authentication.
✅ Validation Level: Very thorough business verification (legal, physical, operational existence)
📄 Certificate Info: Full organization details
👁 Browser Bar: Padlock + organization name in address bar (some browsers now hide this, but cert details still contain it)
💰 Cost: Most expensive
🧰 Use Case: Banks, e-commerce, government portals, high-trust sites
Example:
Address bar: 🔒 [Example Corp] https://example.com
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Purpose: Maximum trust; strictest authentication.
✅ Validation Level: Very thorough business verification (legal, physical, operational existence)
📄 Certificate Info: Full organization details
👁 Browser Bar: Padlock + organization name in address bar (some browsers now hide this, but cert details still contain it)
💰 Cost: Most expensive
🧰 Use Case: Banks, e-commerce, government portals, high-trust sites
Example:
Address bar: 🔒 [Example Corp] https://example.com
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A one-time pad is a cryptographic technique that ensures perfect secrecy, meaning it's mathematically impossible to decrypt a message without knowing the key. It works by using a random key of the same length as the message, encrypting each character or bit of the plaintext with the corresponding character or bit from the key using operations like XOR or modular addition. Crucially, the key is only used once and then discarded.
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📚 OS Concepts — Dining Philosophers Problem 🧵
Let’s solve a dinner table mystery that teaches us all about deadlock and resource sharing 👇
👨🎓 The Setup:
😱 The Problem:
If each picks up their left fork first, they all wait forever for the right fork
→ This causes a deadlock 💥
🔑 Solutions:
✅ Lock Ordering: Always pick lower-numbered fork first
✅ Asymmetric Strategy: Odd picks left-first, even picks right-first
✅ At Most 4 at Table: Prevents total deadlock
✅ Use a Waiter: Central manager checks availability
📌 Core Concepts:
Philosophers = Threads
Forks = Shared Resources
Eat = Critical Section
Think = Non-Critical Work
Deadlock, starvation, and concurrency — all on one dinner table!
#OS #Deadlock #DiningPhilosophers #Semaphores #Concurrency #InfoSecTube
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Let’s solve a dinner table mystery that teaches us all about deadlock and resource sharing 👇
👨🎓 The Setup:
5 philosophers sit around a table 🍽
5 forks placed between them 🍴
To eat, each needs 2 forks (left + right)
After eating → Think → Get hungry again
😱 The Problem:
If each picks up their left fork first, they all wait forever for the right fork
→ This causes a deadlock 💥
🔑 Solutions:
✅ Lock Ordering: Always pick lower-numbered fork first
✅ Asymmetric Strategy: Odd picks left-first, even picks right-first
✅ At Most 4 at Table: Prevents total deadlock
✅ Use a Waiter: Central manager checks availability
📌 Core Concepts:
Philosophers = Threads
Forks = Shared Resources
Eat = Critical Section
Think = Non-Critical Work
Deadlock, starvation, and concurrency — all on one dinner table!
#OS #Deadlock #DiningPhilosophers #Semaphores #Concurrency #InfoSecTube
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🚨 Replay Attack Explained 🔁
A replay attack is a sneaky cyber trick where attackers intercept legit data and resend it to fool systems into thinking it’s real — leading to unauthorized access or action manipulation.
🔍 How It Works:
1️⃣ Interception:
Attacker sniffs data between two parties (e.g. login or transaction).
2️⃣ Re-transmission:
They replay that data to the receiver, pretending to be the legit sender.
3️⃣ Deception:
The receiver gets tricked, thinking it’s valid — and boom 💥, the attacker is in!
📌 Examples:
🔓 Login Replay:
Stealing & reusing login credentials to access accounts.
💸 Transaction Replay:
Duplicating a payment to drain funds or cause confusion.
🛡 Session Replay:
Using stolen session tokens to impersonate users.
🧠 Stay safe! Use encryption, session expiration, and anti-replay mechanisms.
#CyberSecurity #ReplayAttack #InfoSec #HackingExplained #CyberAwareness #StaySecure
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A replay attack is a sneaky cyber trick where attackers intercept legit data and resend it to fool systems into thinking it’s real — leading to unauthorized access or action manipulation.
🔍 How It Works:
1️⃣ Interception:
Attacker sniffs data between two parties (e.g. login or transaction).
2️⃣ Re-transmission:
They replay that data to the receiver, pretending to be the legit sender.
3️⃣ Deception:
The receiver gets tricked, thinking it’s valid — and boom 💥, the attacker is in!
📌 Examples:
🔓 Login Replay:
Stealing & reusing login credentials to access accounts.
💸 Transaction Replay:
Duplicating a payment to drain funds or cause confusion.
🛡 Session Replay:
Using stolen session tokens to impersonate users.
🧠 Stay safe! Use encryption, session expiration, and anti-replay mechanisms.
#CyberSecurity #ReplayAttack #InfoSec #HackingExplained #CyberAwareness #StaySecure
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🔐 What is HOTP? (HMAC-based One-Time Password) 🔁
HOTP is a powerful algorithm used in multi-factor authentication (MFA) to boost your security beyond just passwords.
🧠 It works by generating one-time, unique passwords using:
🔑 A shared secret key
📈 A counter value (increases with each use)
Every time the counter updates, a new password is created — and it’s valid only once. Even if someone sees it, they can't reuse it! 🙅♂️
✅ Why Use HOTP?
🔸 Adds an extra layer of security
🔸 Prevents password reuse
🔸 Great for offline devices (no need for real-time clock)
💡 Used in hardware tokens, MFA apps, and enterprise systems.
#CyberSecurity #HOTP #MFA #OneTimePassword #Authentication #SecureAccess #InfoSec #IdentityVerification #2FA
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HOTP is a powerful algorithm used in multi-factor authentication (MFA) to boost your security beyond just passwords.
🧠 It works by generating one-time, unique passwords using:
🔑 A shared secret key
📈 A counter value (increases with each use)
Every time the counter updates, a new password is created — and it’s valid only once. Even if someone sees it, they can't reuse it! 🙅♂️
✅ Why Use HOTP?
🔸 Adds an extra layer of security
🔸 Prevents password reuse
🔸 Great for offline devices (no need for real-time clock)
💡 Used in hardware tokens, MFA apps, and enterprise systems.
#CyberSecurity #HOTP #MFA #OneTimePassword #Authentication #SecureAccess #InfoSec #IdentityVerification #2FA
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⛑Port mirroring, also known as SPAN (Switched Port Analyzer), is a networking technique where a network switch or router duplicates network packets from one port (the source port) and forwards them to another port (the destination or mirrored port). This allows network administrators to monitor and analyze traffic on a specific port without interrupting normal network operations.
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👍1
💻 4. IV – Individual Validation (for Code Signing)
Purpose: Authenticates individual developers for signing software/code.
✅ Validation Level: Verifies personal identity (via government ID, utility bills, etc.)
📄 Certificate Info: Includes individual's legal name
👁 Prompt: Shows developer’s name when users run signed software
💰 Cost: Varies
🧰 Use Case: Independent developers releasing apps or tools
Example (in a code-signing dialog):
"Publisher: John Doe"
Purpose: Authenticates individual developers for signing software/code.
✅ Validation Level: Verifies personal identity (via government ID, utility bills, etc.)
📄 Certificate Info: Includes individual's legal name
👁 Prompt: Shows developer’s name when users run signed software
💰 Cost: Varies
🧰 Use Case: Independent developers releasing apps or tools
Example (in a code-signing dialog):
"Publisher: John Doe"
📚 OS Concepts — When Do Kernel Modules Run? 🧵
Let’s break down how and when kernel module or device driver code executes!
🔧 A kernel module (like a device driver) is a piece of code that can be loaded/unloaded into the kernel at runtime. But when does it actually run?
✅ It runs when…
🔹 A device or syscall triggers a registered event
🔹 You load the module → insmod → runs init_module()
🔹 You unload the module → rmmod → runs cleanup_module()
🔹 A special file (like /dev/zero) is accessed → the corresponding driver’s function runs
🧠 Example:
Reading from /dev/zero calls the read handler of its device driver.
📌 Takeaway:
Drivers respond to events, they don’t idle or run endlessly!
#Kernel #DeviceDriver #OS
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Let’s break down how and when kernel module or device driver code executes!
🔧 A kernel module (like a device driver) is a piece of code that can be loaded/unloaded into the kernel at runtime. But when does it actually run?
✅ It runs when…
🔹 A device or syscall triggers a registered event
🔹 You load the module → insmod → runs init_module()
🔹 You unload the module → rmmod → runs cleanup_module()
🔹 A special file (like /dev/zero) is accessed → the corresponding driver’s function runs
🧠 Example:
Reading from /dev/zero calls the read handler of its device driver.
📌 Takeaway:
Drivers respond to events, they don’t idle or run endlessly!
#Kernel #DeviceDriver #OS
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