The internet, explained with a courier.

Every attack in the world travels over a network. So today we'll follow one Instagram message from your phone in Hyderabad to a server far away, step by step. Think of it as sending a parcel.

Your message is a parcel

Say you send a photo to your cousin in Dubai. Your phone doesn't send it as one big piece. It cuts it into many small packets, like packing a big order into many small boxes. Each box gets a label: where it's from, where it's going, and its number (box 3 of 50). The boxes may travel by different roads and arrive in a different order, and your cousin's phone puts them back together.

The rules for labelling, sending and re-assembling these boxes are called protocols. The most famous pair is TCP/IP. You don't need to memorise how they work yet, just remember: the internet moves data in small labelled packets.

IP address: the house address

Every device on the internet needs an address so packets know where to go. That address is the IP address, something like 49.205.xx.xx.

But here's a smart trick. Think of an apartment building in Banjara Hills:

• The building has one street address that the courier sees. That's your public IP, given to your home router by Jio, Airtel or ACT.
• Inside, each flat has its own number. Those are private IPs, like 192.168.1.5 for your phone and 192.168.1.8 for your laptop.
• The watchman at the gate receives every parcel and takes it to the right flat. That's your router. (The technical name for this trick is NAT.)

That's why everyone in your house appears to the outside world with the same public IP.

Ports: which door?

Reaching the right building isn't enough. A big post office has many counters: one for parcels, one for money orders, one for passports. On a computer these counters are ports, numbered from 0 to 65,535. Different services wait at different ports:

Remember the nmap command on our homepage? It knocks on every door (port) to see which ones are open. Attackers do this to find a way in. Defenders do it to close doors nobody needs. Same tool, different intention.

DNS: the internet's phonebook

Computers use numbers (IP addresses), but humans remember names like instagram.com. So before your phone can send the parcel, it asks a DNS server: "What's the address for instagram.com?" It's like asking the colony watchman, "Which house is Dr. Rizvi's?"

Now imagine a fake watchman who sends you to the wrong house. That's a real attack (DNS spoofing): you type the right name, but land on a fake site. It's one reason public Wi-Fi can be risky.

HTTP vs HTTPS: postcard vs sealed envelope

With HTTP, your data travels like a postcard: anyone handling it along the way can read it. With HTTPS, it travels in a sealed, locked envelope: people can see where it's going, but not what's inside. That's the padlock in your browser.

Careful, this trips up everyone

The padlock only means the envelope is sealed. It does not mean the person you're sending it to is honest. Scammers can get a padlock for sbi-kyc-update.online in five minutes. Always check the actual website name, not just the padlock.

Game: safe or not?

You're at an Irani café with free Wi-Fi. Look at each situation and decide.