Download Internet Vulnerabilities & Criminal Activities

Internet Vulnerabilities & Criminal
Activities
1.2 – 9/12/2011
Structure of Internet Communications
Computer Data
• Binary format
– All data represented by only 2 signals
– 0’s and 1’s for representation
• 5 means of representation
–
–
–
–
–
Electric current
Voltage
Iron particles
“Pits” and “Land”
Electron grid
• Fragile
• Intangible
– Must have means of interpreting
Protocol
The “language” or rules used
to transmit data over a
network.
Common Protocols
• HTTP - Hypertext Transfer Protocol
• FTP - File Transfer Protocol
• SMTP - Simple Mail Transfer
Protocol
• IP - Internet Protocol
• TCP - Transmission Control
Protocol
• UDP - User Datagram Protocol
Packet
The unit of data sent from a
source to a destination on the
Internet
Packet format
• Header
– Information about
the packet being
sent
• Payload
– Actual data
• Trailer
– End of data signal
– Also used for error
checking
Port
Virtual ports are part of TCP/IP networking.
These ports allow software applications to share
hardware resources without interfering with
each other. Computers and routers
automatically manage network traffic traveling
via their virtual ports. Network firewalls
additionally provide some control over the flow
of traffic on each virtual port for security
purposes.
Common Port Numbers
• 20, 21 - FTP (File Transfer)
• 22 - SSH (Secure Shell)
• 25 - SMTP (Mail)
• 53 - DNS (Domain Name System)
• 80 - HTTP (Web Pages)
Internet Protocol Number
Numerical identification
number used by a node on
the Internet
IP Number Format
• IPv4 - 32 bits, 4 bytes long
• Each byte separated by a . (dot)
• Example - 64.252.150.126
• Divided in to classes by first octet
– Class A , 1-126
– Class B, 128-191
– Class C, 192-223
– 127.0.0.1, loopback
IPv6
• Succeeds IPv4
• Many more unique numbers
available
• 128 bit addresses – 2128
possible addresses
• Eliminates need for NAT
• Offers more features than
IPv4
• Typical IPv6
address:2001:0db8:85a3:000
0:0000:8a2e:0370:7334
Domain Name System
(DNS)
A server that converts domain
names into their associated IP
number
64.252.150.126 = snet.net
OSI - Open Systems Interconnection
• Model of network
protocols
• Created by the ISO
• Protocol stack
• Each layer
responsible for
specific processing
• Layers only
communicate with
layer above & layer
below
• Communications
– Outgoing - each layer
adds new data
– Receiving - each layer
strips off data
7 - Applications Layer
• Interface between applications
program and protocol stack
• Layer contacted by application
program
• Examples - http, ftp, smtp
6 - Presentation Layer
• Also called translation layer
• Converts data received from
application layer to format used by
protocol stack
• Can be used for compression &
encryption
5 - Session Layer
• Allows two programs within
different computers to establish a
communication session
• Sets communication markers (not
on all networks)
4 - Transport Layer
• Interface between application layers
and network layers
• Protocols - tcp, udp
• On sending machine:
– Divides data sent by Session layer into
packets
• On receiving machine:
– Puts packets into order
– Checks data integrity
– Sends acknowledgement
3 - Network Layer
• Handles packet addressing
• Converts logical address to
physical address
• Sets route packets will follow from
source to destination
• Protocol - IP
2 - Data Link Layer
• Sending machine
– Converts packets into frames
– Adds physical address of source and
destination machines
– Calculates checksum
• Receiving machine
– Recalculate checksum
– Send acknowledgement if checksums match
1 - Physical Layer
• Sending machine
– Converts Data Link Layer frames into
transmission signals
• Electronic signal
• Luminous signal
• Electromagnetic signal
• Receiving machine
– Converts physical signal into 1’s & 0’s
OSI - How it works
• Sending machine each layer adds a
header
• Receiving machine each layer removes
a header
• Layer only sees
header added by
same layer on
sending machine
TCP/IP
• Fewer layers than
OSI
• Different
protocols working
on different level
• May have more
than one protocol
on the same level
Application Layer
• Communicates
between
application
programs &
transport layer
• Protocol selected
• Port number
assigned
Transport Layer
• Divides data into
packets
• Orders received
packets
• Checks &
acknowledges
received packets
Transport Layer Protocols
• TCP - Transmission
Control Protocol
– Reliable
– Used for SMTP, HTTP,
FTP
• UDP - User
Datagram Protocol
– Unreliable
– Used for DNS
Internet Layer
• Determines path
packet should take
from source to
destination
• Every router on the
path is called a hop
• Router uses its
router table to
determine packet’s
path
• No
acknowledgement on
this level
Network Interface Layer
• Most common physical
network - Ethernet
• Logic Link Control (LLC)
Layer
– Adds information on
Internet layer protocol
• Media Access Control
(MAC) Layer
– Add source & destination
MAC address
• Physical Layer - same as
OSI model Physical Layer
Network Interface Frame
• Data to be
transmitted or
received has now
been converted to a
frame
• Each layer adds a
header when
sending
• Each layer removes
a header when
receiving
Communications Log
Languages of the Web - HTML
• HyperText Markup Language
– File extensions: .html, .htm, .html4
– Comprised of elements which tells
receiving browser how to display those
elements
– Hyperlink: link from a web page element to
another file or web page
– Some elements can pose security risks
– Related: Dynamic HTML (DHTML), XML,
XHTML
Languages of the Web - Perl
• Practical Extraction and Report
Language
– File extension: .pl
– High level programming language
– Portable, free
– Robust & flexible
– Server-side actions
– Security risk from inputs
Languages of the Web - PHP
• Personal Home Page
– File extensions: .php, .php3
– Server-side scripting language
– Used for database applications
– Security risk from inputs
Languages of the Web - ColdFusion
• ColdFusion
– File extension: .cfm
– Three major components
• ColdFusion Application Server - server-side
processor of ColdFusion page requests
• ColdFusion Markup Language - similar to HTML
• ColdFusion Studio - integrated development
environment (IDE)
• Can be used for database connectivity
Languages of the Web - ASP
• Active Server Pages
– File extension: .asp
– Server-side scripting environment
– Default language is VBScript
– Can be used for database
connectivity
– ActiveX - used for dynamic web page
content
Languages of the Web - CGI
• Common Gateway Interface
– File extensions: .cgi, .pl
– Oldest standard for passing
information from web server to
another program (such as Perl)
– Set of guidelines used with many web
languages
Languages of the Web - Java
• Java
– File extension: none
– Client-based
• Scripting languages
– Javascript - connected to Java by name only
– Jscript - Microsoft’s Javascript clone
– Server-based
• Java Server Pages (JSP)
– File extension: .jsp
– Used for dynamic content & database connectivity
• JHTML
– File extension: .jhtml
– HTML with Java
Sources
• “The OSI Reference Model for Network Protocols” by
Gabriel Torres. Hardware Secrets. (2007)
http://www.hardwaresecrets.com/article/431
• “How TCP/IP Protocol Works - Part 1” by Gabriel Torres.
Hardware Secrets. (2007)
http://www.hardwaresecrets.com/article/433
• “How TCP/IP Protocol Works - Part 2” by Gabriel Torres.
Hardware Secrets. (2007)
http://www.hardwaresecrets.com/article/435
• “Languages of the Web” by Stuart McClure, Saumil
Shah, and Shreeraj Shah. Web Hacking: Attacks and
Defenses (2003)