import hashlib

original = b"Invoice: pay Rs 5000 to account 1234"
altered  = b"Invoice: pay Rs 5000 to account 9999"

print(hashlib.sha256(original).hexdigest()[:16])
print(hashlib.sha256(altered).hexdigest()[:16])
# A tiny change gives a completely different hash,
# so comparing hashes reveals tampering.

Which CIA goal is affected?
1. A laptop with customer data is stolen        → Confidentiality
2. Exam marks are changed in a database        → Integrity
3. Ransomware locks all office files           → Availability (and often confidentiality)
4. A server crashes from too much traffic      → Availability
5. A phishing email steals a login             → Confidentiality first, then possibly all three

Before clicking any link in an email or SMS:
☐ Is the sender address exactly right? (not paypa1.com, not a free email)
☐ Is it creating urgency or fear? ('account blocked in 2 hours')
☐ Does the link go where it says? (hover or long-press to preview)
☐ Is it asking for OTP, password or card details? (real banks do not)
☐ Did I expect this message?
If unsure: open the official app or website yourself instead of the link.

import math

def guesses(charset_size, length):
    return charset_size ** length

# 8 lowercase letters vs a 4-word passphrase from a 7776-word list
print(f"{guesses(26, 8):.2e}")     # about 2.09e+11
print(f"{guesses(7776, 4):.2e}")   # about 3.66e+15
# Longer passphrases are far harder to guess and easier to remember.

# Count failed SSH logins per IP on a Linux server you manage
# (Debian/Ubuntu log path; other systems use journalctl)
grep "Failed password" /var/log/auth.log \
  | awk '{print $(NF-3)}' \
  | sort | uniq -c | sort -rn | head
# Many failures from one IP suggests a password-guessing attempt.

Simple incident response steps
1. Prepare   — know who to call, keep backups and contacts ready
2. Identify  — confirm something is wrong; record what you see
3. Contain   — disconnect affected devices, reset compromised passwords
4. Eradicate — remove malware, close the weakness used
5. Recover   — restore from clean backups, monitor closely
6. Learn     — write what happened and what to change

Personal Security Checklist
☐ Unique password for email, banking and social media
☐ Password manager installed
☐ MFA on email and banking
☐ Phone and laptop auto-update turned on
☐ Screen lock with PIN/biometric
☐ Backups of photos and documents
☐ Never share OTPs with anyone
☐ Apps only from official stores

Small Office Security Checklist
☐ Separate accounts for each person; no shared logins
☐ Admin rights only for IT person
☐ Wi-Fi with WPA2/WPA3 and a strong password; guest network separate
☐ Updates on all PCs and the router
☐ Daily backups, one copy offline
☐ Basic phishing awareness session for staff
☐ Written plan: who to call if something goes wrong

Beginner Cybersecurity Roadmap
Step 1: Computer and networking basics (IP, DNS, ports)
Step 2: Linux and Windows basics
Step 3: Security fundamentals (CIA, threats, controls)
Step 4: Hands-on labs on practice platforms
Step 5: Choose a path — SOC/defence or testing/offence
Step 6: Projects, write-ups and an entry-level certification