The Internet
(Computer Networking)
● In what ways do we use the Internet for?
● Fun facts about the Internet
○
○
Almost impossible to measure how much
data you can access on the Internet
Estimated to take about 1,000,000,000
people’s brain to store all the data on the
Internet.
What is the Internet?
What is the Internet?
● consists of collection of computers and
related devices (such as: smartphones,
tablets, etc)
● These communicate with each other
○ through wired and wireless technologies
○ to allow us to share information
What is the Internet?
each of these are routers
Another
Machine
Your
Laptop
The Internet
● How does it work?
How does it allow us to send or share
information?
○
○
How do machines communicate with another
machine?
Similar to calling a friend using the phone with
the contacts saved
○
● This is true in networking also
www.google.
com
you
internet
● domain name
○ name of a website (ex: google.com)
● IP address (Internet Protocol address)
○ Each machine has an IP address
What about return address?
What about return address?
- Your own machine’s IP address
IP exercises
Using the command: ifconfig
● The ifconfig command is often used to view or
modify a computer’s IP address.
Your machine’s IP address is very important because it is used for
receiving information so the other machine knows where to send
back data.
Hands-on Exercise 1:
You will use the ifconfig command to retrieve the IP address of the computer you are using.
First, you have to open the Command Prompt:
Step 1. Click on Dashboard, and then type Terminal.
Next, you type in the command:
Step 2. At the command prompt, enter:
ifconfig
The IP address will be a series of numbers following the pattern xxx.xxx.xxx.xxx (i.e.,
156.56.27.32).
Step 3. What is the IP address of your computer?
Step 4. Is it different than from your peers?
Example screen:
How does your machine figure out an IP address of a given
domain name?
● Your browser extracts the domain name and sends it to DNS (Domain Name
System).
● DNS acts as an address book and translates this to an IP address
● Your machine tries to contact this IP address
Domain name: www.google.com
Web
browser
Domain Name
Server
DNS
IP address:
208.77.188.166
You
Google
server
IP address
Domain name to IP address exercise
Lesson 1.2 Using the command: nslookup
● nslookup - lets you look up an IP address
given a domain name like “www.google.
com”
Hands-on Exercise:
You are going to use nslookup to lookup the IP address of a website of your choice.
Step 1. At the command prompt, type:
nslookup website
again replacing website with the website you chose (e.g, nslookup google.com).
Step 2. How many IP addresses did you find for your website?
Step 3. Now copy one of the IP addresses and paste it to your browser and hit enter. What
did you get?
Step 4. Is it same as typing the domain name( the website name) and hitting enter?
Step 5. Even though the results are same, what is the difference?
Example screen:
Router
-- You will need a fastest path for two machines to
communicate.
-- A device called router is used for this.
each of these are routers
Another
Machine
Your
Laptop
The Internet
● The routers decide how to get your message
across the Internet.
● And then it forwards your message with the given
destination
● The routers decide how to get your message
across the Internet.
● What would be an efficient path here?
○ 1 -> 2 -> 4
3
2
facebook.com
1
4
5
you
7
internet
6
Traceroute exercises
Lesson 1.3
● tracepath - lets you see the routers that
forward your message to a given
destination
Hands-on Exercise:
We will find how many routers it takes to transfer information from your computer to
a website of your choice.
Step 1. Go to website www.yougetsignal.com/tools/visual-tracert
Then replacing website with the domain name of the website you chose (e.g, tracepath
google.com).
Step 2. How many routers forward messages sent from your computer to the website
you chose?
Step 3. Do you think you would see the same number of routers if you tried this at
home?
http://en.dnstools.ch/visual-traceroute.html
Computer Security
Good security standards follow 90/10 rule
- 10% of security safeguards are technical
- 90% of security safeguards rely on the
computer user - “YOU”
How??
Types of Security Threats:
1. Social Engineering - an attacker uses human
interaction (social skills) to obtain or compromise
information about you
Examples - Security question
- Type of password
http://zed0.co.uk/crossword/
2. Phishing Attack legitimate-looking
email/webpage in an
attempt to gather
personal and financial
information from
recipients - SF Giants!
https://www.youtube.
com/watch?
v=gTApmz_ybus
Legitimate or not??
Legitimate or not??
How to protect yourself when on a public computer?
- Don’t save your login information or enter sensitive information
into a public computer
- Don't leave the computer unattended with sensitive information on
the screen
- Erase your tracks, clear cookies - https://www.youtube.
com/watch?v=ZP7ebyqBn_M
Safety Tips
- Have different passwords for all your different
accounts
- Never have your name or a common word in your
password
- Never share your password with anyone
- Always have alpha-numeric as well as a few special
characters in your password
Common passwords - http://www.huffingtonpost.
com/2014/01/22/most-common-passwords2013_n_4646352.html
1. Be aware of suspicious phone calls, text messages, or
email messages from individuals asking about your
information.
2. Do not provide personal/financial information unless
you are certain of a person's authority to have the
information.
3. Don't send sensitive information over the Internet
before checking a website's security
https://mail.google.com
5. Pay attention to the URL of a website. Malicious
websites may look identical to a legitimate site, but
the URL may use a variation in spelling or a different
domain (e.g., .com vs. .net).
6. If you are unsure whether an email request is
legitimate, do not click on it.
7. Install and maintain anti-virus software, firewalls,
and email filters to reduce some of this traffic
https://www.youtube.com/watch?v=gTApmz_ybus