DIAGRAMA DE FLUJO

Es la representación grafica de un algoritmo.

Dados tres números determinar si la suma de una pareja de ellos es igual al tercer numero, si se cumple esta condición escribir iguales y en caso contrario escribir distintos.

3 9 6 iguales

3 + 6 = 9


2 3 4 distintos

2 + 4 = 6

algoritmo:
Pedir los tres valores.
Asignar el primer valor a A
Asignar el segundo valor a B
Asignar el tercer valor a C
Si A+B=C escribir "iguales" e ir a fin.
Si A+C=B escribir "iguales" e ir a fin.
Si B+C=A escribir "iguales" e ir a fin.
Escribir distintos e ir "diferentes"

¿QUE ES UN ALGORITMO?

ALGORITMO
Es un método para resolver un problema mediante una serie de pasos definidos, precisos y finitos.

Preciso: implica el orden de realización de cada uno de los pasos

Definido: si se sigue dos veces, se obtiene el mismo resultado.

Finito: Tiene un numero determinado de pasos, implica que tiene un fin.

EJEMPLO:
Ingredientes:

(6 porciones)

½ taza de azúcar para hacer el caramelo
4 huevos
½ taza de agua
½ taza de azúcar esta es para el flan
1 2/3 de leche evaporada
2 cucharaditas de vainilla

Preparación:

En un molde para flan vacié la primera ½ taza de azúcar, colóquelo sobre el fuego y deje que se derrita el azúcar. Ladee el molde para que cubra bien el fondo y las paredes.
Aparte licue los huevos, la otra medita taza de azúcar, el agua, la leche evaporada y la vainilla. Vacíe sobre el caramelo.
Tape el molde con un trozo de papel aluminio y hornee a baño María durante 35 o 40 minutos.
Refrigere y desmolde.

Enseñando a un niño a atarse las agujetas

Asegurarse que cada hollo del tennis este ocupado por las agujetas.
Sostener cada ambos extremos de la agujeta con su mano correspondiente.
Doblar los extremos a la mitad en forma de ovalo, asegurarse que quede amplio.
Juntar los óvalos formados por los extremos, luego entrecruzamos. Aprietalos bien y listo!

CAPITULO 8

Once the hacker gains access to the network, four types of threat may arise:

INFORMATION THEFT
breaking into a computer to obtain confidential information. Info can be used or sold for various purposes.Example:stealing a organization´s proprietary info, such as research and development info.

DATA LOSS AND MANIPULATION
breaking into a computer to destroy or alter data records.Examples of date loss:sending a virus that reformats a computer´s hard drive. Examples of data manipulation:breaking into a records system to change information, such as the price of an item.

IDENTITY THEFT
a form of info theft where personal info is stolen for the purpose of taking over someone´s identity. Using this info an individual can obtain legal documents, apply for credit and make unauthorized online purchases.Identity theft is a growing problem costing billions of dollars per year.

DISRUPTION OF SERVICE
preventing legitimate users from accessing services to which they should be entitled.



External Threats
arise from individuals working outside of an organization. They do not have authorized access to the computer systems or network.

Internal threats
occur when someone has authorized access to the network through a user account or have physical access to the network equipment.

SOCIAL ENGINEERING
Techniques uesd by an attacker to manipulate ussuspecting people into providing info or computer system access.
techiniques:
PRETEXTING
fraudulent acquisition of sensitive info, primarily over the telephone, where an invented scenario persuades a target of legitimacy.

PHISHING
fraudulent acquisition os sensitive info through the impersonation of a trustworthy source.

VISHING
fraudulent aquisition of sensitive info through VoIP that terminates in a computer.

VIRUSes
It needs to be activated. Once activated, a virus may do nothing more than replicate itself and spread.A more serious virus may be programmed to delete or corrupt specific files before spreading. Viruses can be transmitted via email attachments, downloaded files, instant messages or via diskette, CD or USB devices.

Worms
Uses the network to send copies of itself to any connected hosts.Do not necessarily require activation or human intervention.

Trojan Horses
is a non-self replicating program that is written to appear like a legitimate program, when in fact it is an attack tool.It may be relatively harmless or can contain code that can damage the contents of the computer's hard drive.Can also create a back door into a system allowing hackers to gain access.



Denial of Service (DoS)

Attacks on an individual computer or groups of computers with the intent to deny services to intended users. DoS attacks can target end user systems, servers, routers, and network links.

In general, DoS attacks seek to:

Flood a system or network with traffic to prevent legitimate network traffic from flowing
Disrupt connections between a client and server to prevent access to a service

Types of Dos attacks:

SYN (synchronous) Flooding: a flood of packets are sent to a server requesting a client connection. The packets contain invalid source IP addresses. The server becomes occupied trying to respond to these fake requests and therefore cannot respond to legitimate ones.

Ping of death: a packet that is greater in size than the maximum allowed by IP (65,535 bytes) is sent to a device. This can cause the receiving system to crash.

DDoS
It is designed to saturate and overwhelm network links with useless data.Operates on a much larger scale than DoS attacks.The attack points may be unsuspecting computers that have been previously infected by the DDoS code.The systems that are infected with the DDoS code attack the target site when invoked.

Brute force attack
Is another type of attack.
A fast computer is used to try to guess passwords or to decipher an encryption code. The attacker tries a large number of possibilities in rapid succession to gain access or crack the code. Brute force attacks can cause a denial of service due to excessive traffic to a specific resource or by locking out user accounts.



SPYWARE
a malicious program, typically installed without a user's knowledge, designed to perform tasks such as capture keystrokes, for the benefit of the originator of the program.

POPUP
a form of online advertising to increase web traffic or capture e-mail addresses that displays when a user opens certain websites or clicks on specific links.

COOKIES
are a form of spyware. They are used to record information about an Internet user when they visit websites.May be useful or desirable by allowing personalization and other time saving techniques. Many web sites require that cookies be enabled in order to allow the user to connect.

ADWARE
is a form of spyware used to collect information about a user based on websites the user visits.Is commonly installed by a user in exchange for a "free" product. When a user opens a browser window, Adware can start new browser instances which attempt to advertize products or services based on a user's surfing practices. The unwanted browser windows can open repeatedly, and can make surfing the Internet very difficult, especially with slow Internet connections.

SPAM
unsolicited or junk e-mail messages sent to multiple recipients for either legitimate or fraudulent purposes.

SECURITY TOOLS

Firewall
controls traffic to and from a network.

Spam filter
software installed on an end-user workstation or server to identify and remove unwanted emails.

Patches and Updates
software applied to an OS or application to correct a known security vulnerability or add functionality.

Anti-spyware
to detect and remove spyware and adware.

Popup blocker
to prevent popups and unders.

Anti-virus
to detect and remove viruses, worms and Trojan.

Some of the signs that a virus, worm or Trojan horse may be present include:

Computer starts acting abnormally
Program does not respond to mouse and keystrokes
Programs starting or shutting down on their own
Email program begins sending out large quantities of email
CPU usage is very high
There are unidentifiable, or a large number of processes running
Computer slows down significantly or crashes

Features that can be included in Anti-virus programs are:

Email checking - Scans incoming and outgoing emails, and identifies suspicious attachments.
Resident dynamic scanning - Checks executable files and documents when they are accessed.
Scheduled scans - Virus scans can be scheduled to run at regular intervals and check specific drives or the entire computer.
Automatic Updates - Checks for, and downloads, known virus characteristics and patterns. Can be scheduled to check for updates on a regular basis.

Actions to prevent the spread of spam include:

Apply OS and application updates when available.
Run an Antivirus program regularly and keep it up to date.
Do not forward suspect emails.
Do not open email attachments, especially from people you do not know.
Set up rules in your email to delete spam that by-pass the anti-spam software.
Identify sources of spam and report it to a network administrator so it can be blocked.
Report incidents to the governmental agency that deals with abuse by spam.

A Firewall is one of the most effective security tools available for protecting internal network users from external threats.Controls the traffic between them as well as helps prevent unauthorized access. Firewall techniques

Packet Filtering - Prevents or allows access based on IP or MAC addresses.

Application Filtering - Prevents or allows access to specific application types based on port numbers.

URL Filtering - Prevents or allows access to websites based on specific URLs or keywords.

Stateful Packet Inspection (SPI) - Unsolicited packets are blocked unless permitted specifically. SPI can also include the capability to recognize and filter out specific types of attacks such as DoS.

Firewall products come packaged in various forms:

Appliance-based firewalls -is built-in to a dedicated hardware device known as a security appliance.

Server-based firewalls -consists of a firewall application that runs on a network operating system (NOS) such as UNIX, Windows or Novell.

Integrated Firewalls -implemented by adding firewall functionality to an existing device, such as a router.

Personal firewalls -reside on host computers and are not designed for LAN implementations. They may be available by default from the OS or may be installed from an outside vendor.

USING A FIREWALL




ONE FIREWALL CONFIG
external network
internal network
DMZ.
To monitor the traffic and determine what traffic should be passed to the DMZ,internally, and what should be denied altogether.

TWO FIREWALL CONFIG
There is an internal and external firewall with the DMZ located between them.
A two-firewall configuration is more appropriate for larger, more complex networks that handle a lot more traffic.

ACTIVIDADES CAP 7

INFOGRAMA

La infografía es una representación más visual que la propia de los textos, en la que intervienen descripciones, narraciones o interpretaciones, presentadas de manera gráfica normalmente figurativa, que pueden o no coincidir con grafismos abstractos y/o sonidos. La infografía nació como un medio de trasmitir información gráficamente. Los mapas, gráficos, viñetas, etc. son infogramas, es decir unidades menores de la infografía, con la que se presenta una información completa aunque pueda ser complementaria o de sintesis.

Hay ciertos elementos básicos que se deben tomar en cuenta al diseñar una infografía, como lo son:

La proporción:
es el recorrido de un plano en movimiento que se convierte en un volumen. Debe ser correcta y tener cuidado al agrandar una forma porque puede quedar distorsionada. Es decir, la imagen tiene que ser extendida en sus dos dimensiones (alto y ancho) proporcionalmente.

La perspectiva:
nos ayuda a representar la realidad y crear efectos volumétricos. Puede un gráfico ser más atractivo cunado se aplica este elemento básico del diseño .Se debe ser cuidadoso con ella, respetando las respectivas medidas que se le otorga. A pesar de vivir en un mundo tridimensional, la bidimensionalidad se entiende mejor en la página impresa.

Las texturas:
consisten en la modificación o variación de la superficie de los materiales utilizados, ya sea de una forma visual o táctil. En los diseños, si no se utilizan bien pueden causar confusiones o ilusiones ópticas.

Las formas:
hablamos de forma cuando el trazo de línea se une en un mismo punto. Sus características son estáticas o dinámicas dependiendo del uso que se les de.

Las formas más básicas del diseño son: el círculo, el rectángulo y el triángulo.

El plano:
permite fragmentar y dividir el espacio, de esta forma podemos delimitar y clasificar las diferentes zonas de nuestra composición.

El movimiento:
es uno de los elementos visuales que implica y dota de más fuerza a un gráfico. Una fotografía capta con mayor facilidad este elemento. Pero en un dibujo, el diseñador debe buscar los elementos necesarios como líneas rectas, sombras, curvas, repetición, etc. para lograr el efecto.

El color:
es uno de los elementos fundamentales y más evidentes del diseño y que puede dar carácter y significado a las imágenes que se les aplica. En las artes gráficas tenemos dos grandes categorías con respecto al color que son: imagen a color e imagen en blanco y negro.

Paratexto:
El término paratexto designa al conjunto de los enunciados que rodean a un texto: el título, subtítulos, prefacio, indicación de insertar, índice de materias, etc. El paratexto está destinado a hacer presente el texto, asegurar su presencia en el mundo, Se distingue el paratexto de autor y el paratexto editorial. El primero es producido por el autor (su nombre, epígrafe, prefacio, dedicatoria, nota al pie de página) y el segundo al editor (tapa, catálogo, copyright, etc.).


mi infografia sera de HAIR MYHTS

Capitulo 7

GLOSSARY

RF:
radio frequency. electromagnetic waves generated by AC and sent to an antenna within the electromagnetic spectrum.

IrDA:
infrared data association. defines protocol standards for the short range exchange of data over infrared light for uses such as PANs.

ISM:
industrial, scientifical and medical bands. Radio bands defined by the ITU-R in 5.150of the Radio Regulations and share with license-free, erro-tolerant communications applications such as wireless LANs and Bluetooth.

Bluetooth:
Wireless industry standard that uses an unlicensed radio frequency for short-range communication enabling portable devices to communicate over chort distances.

WLAN:
wireless local area network. Two or more computers or devices equipped to use spread-spectyrum technology based on radio waves for communication within a limited area.

encryption:
The application of the specific algorithm so as to alter the appearence of the data making it incomprehensive to those who are not authorized to see the information.

authentication:
Aprocess implemeted on a netwotk to verify the identify of a user.

troughput:
The rate at which a computer or network sends or receives data meassured in bits per second(bps).

wireless client:
Any host device that can connect to a wireless network.

STA:
Abbreviation for STAtion, a basic network device.

SSID:
service set identifier. The code assigned to a packet that designates that the communication is part of a wireless network.

IBSS:
independent basic service set. an 802.11 network comprised of a collection os stations that communicate with each other, but not with a network infrastructure.

BSS:
basic service set. A group of 802.11 devices connected to an access point.

ESS:
extended service set. A colection of BSSs that communicate with one another through the distribution system (usually the wired Ethernet port on an access point).

CSMA/CA:
carrier sense multiple access with collision avoidance.The basic medium access for 802.11 wireless network.

RTS:
request to send. Along with clear to send, is used by the 802.11 wireless networking protocl to reduce frame collision introduced by hidden terminal problem and exposed node problem.

CTS:
clear to send.Along with request to send, is used by the 802.11 wireless networking protocol to reduce frame collisions introduced by the hidden terminal problem and exposed node problem.

ACK:
Acknowledgement. A transmission control character(or a transmission frame) that confirms a transmitted message was received un corrupted without errors or that receiving station is ready to accept transmissions.

MAC filtering:
Access control method that permits and denies network access based on MAC addresses ti specific devices through the use of blacklists and whitelists.

open aithentication:
A type of wireless authentication where any and all clients are able to associate regardless of who they are.

PSK:
pre-shared key. A secret shared between the wireless AP and a client to control access on a network.

EAP:
Extends Authentication Protocol. An authentication framework, not a specific autjentiction mechanism. Most commonly used in wireless LANs, EAP provides common functions and a negociation of the desired authentication mechanism.

RADIUS:
remote authentication dial in user service.An AAA(authentication, authorization, and accounting) protocol used for security applications, such as network access or IP mobility. It authenticates users and machines in both local and remote aituations.

WEP:
Wired Equivalent Privacy. Part of the IEEE 802.11 wireless networking standard that provides a low level of security.

WPA: Wi-Fi Protected Access. Developed to adress security issues in WEP. Provides higher level of security in a wireless network.

firmware:
Software embedded in a hardware device typically provided on flash ROMs or as a binary image file that can be uploaded onto existing hardware by a user.

site survey:
Software installed servers and desktop computers that provides threat protection capabilities.

DIFERENT STANDRDS

802.11a
Uses 5 GHz RF spectrum
Not compatible with 2.4 GHz spectrum, i.e. 802.11 b/g/n devices
Range is approximately 33% that of the 802.11 b/g
Relatively expensive to implement compared to other technologies
Increasingly difficult to find 802.11a compliant equipment

802.11b
First of the 2.4 GHz technologies
Maximum data-rate of 11 Mbps
Range of approximately 46 m (150 ft) indoors/96 m (300 ft) outdoors

802.11g
2.4 GHz technologies
Maximum data-rate increase to 54 Mbps
Same range as the 802.11b
Backwards compatible with 802.11b

802.11n
Newest standard in development
2.4 GHz technologies (draft standard specifies support for 5 GHz)
Extends the range and data throughput
Backwards compatible with existing 802.11g and 802.11b equipment (draft standard specifies 802.11a support)

ANTENNAS:

Used on APs and Wireless bridges
Increases the output signal strength from a wireless device
Receives wireless signals from other devices such as STAs
Increase in signal strength from an antenna is known as the gain
Higher gains usually translate into increased transmission distances.

CLIENT:
also known as a STA
a mobile device that can participate in the wireless LAN

AP:
converts Ethernet Frame type to 802.11 format
controls acces by wireless clients into the wired LAN.

BRIDGE:
allows range wireless communication.

CHAPTER 6

A web server and a web client use specific protocols and standards in the process of exchanging information to ensure that the messages are received and understood. These protocols cover: application, transport, Internetwork and network access protocols.

Application Protocol

Hypertext Transfer Protocol (HTTP) governs the way that a web server and a web client interact. HTTP defines the format of the requests and responses exchanged between the client and server. HTTP relies on other protocols to govern how the messages are transported between client and server.

Transport Protocol

Transmission Control Protocol (TCP) is the transport protocol that manages the individual conversations between web servers and web clients. TCP formats the HTTP messages into segments to be sent to the destination host. It also provides flow control and acknowledgement of packets exchanged between hosts.

Internetwork Protocol

The most common internetwork protocol is Internet Protocol (IP). IP is responsible for taking the formatted segments from TCP, assigning the logical addressing, and encapsulating them into packets for routing to the destination host.

Network Access Protocols

Network access protocols perform two primary functions:

Data link management protocols take the packets from IP and encapsulate them into the appropriate frame format for the local network. These protocols assign the physical addresses to the frames and prepare them to be transmitted over the network.

The standards and protocols for the physical media govern how the bits are represented on the media, how the signals are sent over the media, and how they are interpreted by the receiving hosts. Network interface cards implement the appropriate protocols for the media that is being used.

TCP

When an application requires acknowledgment that a message is delivered, it uses TCP.

TCP breaks up a message into small pieces known as segments. The segments are numbered in sequence and passed to IP process for assembly into packets. TCP keeps track of the number of segments that have been sent to a specific host from a specific application. If the sender does not receive an acknowledgement within a certain period of time, it assumes that the segments were lost and retransmits them. Only the portion of the message that is lost is resent, not the entire message.

On the receiving host, TCP is responsible for reassembling the message segments and passing them to the application.

FTP and HTTP are examples of applications that use TCP to ensure delivery of data.


The TCP slows down information transfer. In those cases, UDP may be a more appropriate transport protocol.

UDP is a 'best effort' delivery system that does not require acknowledgment of receipt.It is not guaranteed that the letter is received, but the chances are good.

UDP is preferable with applications such as streaming audio, video and voice over IP (VoIP).

An example of an application that uses UDP is Internet radio. If some of the message is lost during its journey over the network, it is not retransmitted. If a few packets are missed, the listener might hear a slight break in the sound. If TCP were used and the lost packets were resent, the transmission would pause to receive them and the disruption would be more noticeable.

PORTS
Is used to keep track of specific conversations and destination services requested. Every message that a host sends contains both a source and destination port.

Destination Port

The client places a destination port number in the segment to tell the destination server what service is being requested.

Source Port

This allows multiple conversations to occur simultaneously. In other words, multiple devices can request HTTP service from a web server at the same time. The separate conversations are tracked based on the source ports.

SOCKET
is used to identify the server and service being requested by the client

Domain Name System (DNS)
Provides a way for hosts to use this name to request the IP address of a specific server. DNS names are registered and organized on the Internet within specific high level groups, or domains. Some of the most common high level domains on the Internet are .com, .edu, and .net.

When the DNS server receives the request, it checks its table to determine the IP address associated with that web server. If the local DNS server does not have an entry for the requested name, it queries another DNS server within the domain. When the DNS server learns the IP address, that information is sent back to the client. If the DNS server cannot determine the IP address, the request will time out and the client will not be able to communicate with the web server.

When a web client receives the IP address of a web server, the client browser uses that IP address and port 80 to request web services. This request is sent to the server using the Hypertext Transfer Protocol (HTTP).

The information content of a web page is encoded using specialized 'mark-up' languages. HTML (Hypertext Mark-up Language) is the most commonly used but others, such as XML and XHTML, are gaining popularity.

The HTTP protocol is not a secure protocol; information could easily be intercepted by other users as it is sent over the network.


The File Transfer Protocol (FTP)
Provides an easy method to transfer files from one computer to another.

FTP server enables a client to
Exchange files between devices
manage files remotely by sending file management commands such as delete or rename It uses two different ports to communicate between client and server

To begin an FTP session it uses port 21. Once the session is opened, the server will change to port 20 to transfer the data files.

EMAILS
Various application protocols used in processing email include SMTP, POP3, IMAP4.


Simple Mail Transfer Protocol (SMTP)

Used by an email client to send messages to its local email server. The local server then decides if the message is destined for a local mailbox or if the message is addressed to a mailbox on another server.
SMTP requests are sent to port 25.


Post Office Protocol (POP3)

A server that supports POP clients receives and stores messages addressed to its users. When the client connects to the email server, the messages are downloaded to the client.Messages are not kept on the server after they have been accessed by the client. Clients contact POP3 servers on port 110.

Internet Message Access Protocol (IMAP4)

It does the same that POP3, but IMAP keeps the messages unless its users errase them.
It requests on port 143.


The following are typical entries when configuring an email client:

POP3 or IMAP4 Server name
SMTP Server name
Username
User password
SPAM and Virus filters

A call to a regular telephone (land line or cell phone) requires the use of a gateway to access the Public Switched Telephone Network (PSTN).

PORTS
Help servers to know which service is being requested by a client.

Are assigned and managed by the Internet Corporation for Assigned Names and Numbers (ICANN).

Well-Known Ports

Destination ports that are associated with common network applications. These ports are in the range of 1 to 1023.

Registered Ports

Ports 1024 through 49151 can be used as either source or destination ports. These can be used by organizations to register specific applications such as IM applications.

Private Ports
Ports 49152 through 65535, often used as source ports. These ports can be used by any application.


layered model
Depicts the operation of the protocols occurring within each layer, as well as the interaction with the layers above and below it.

Benefits:

*Assists in protocol design.
*Fosters competition because products from different vendors can work together.
*Prevents technology or capability changes in one layer from affecting other layers above and and below.
*Fosters competition because products from different vendors can work together.
*Prevents technology or capability changes in one layer from affecting other layers above and below.
*Provides a common language to describe networking functions and capabilities.

TCP/IP MODEL
It specify the interaction of each protocol

OSI MODEL
Includes all functions, or tasks, associated with Inter-network communications, not just those related to the TCP/IP protocols. Compared to the TCP/IP model, which only has four layers, the OSI model organizes the tasks into seven more specific groups. A task, or group of tasks, is then assigned to each of the seven OSI layers.

APPLICATION LAYER:
define interfaces between application software and network communication functions.
provides standardized services such as file transfer between systems.

PRESENTATION LAYER:
standardizes user data formats for use between different types of systems.
encodes and decodes user data; encrypts and decrypts data; compresses and and decompresses data.

SESSION LAYER:
manages user sessions and dialogues.
mantains logical links between systems.

TRANSPORT LAYER:
manages end-to-end message delivery over the network.
can provide reliable and sequential packet delivery through error recovery and flow control mechanisms.

NETWORK LAYER:
routes packets according to unique network devices addresses.

DATA LINK LAYER:
defines procedures for operating the communications links.
detects and corrects frame transmit errors.

PHYSICAL LAYER:
defines physcial means of sending data over network devices.
interfaces between network medium and devices.
defines optical, electrical and mechanical characteristics.














The Packet Tracer (PT)allows viewing of simulated data being transmitted between two hosts. It uses Protocol Data Units (PDUs) to represent network traffic frames and displays protocol stack information at the appropriate layers of the OSI model.

Layer 1 (Physical): Fast Ethernet port

Layer 2 (Data Link): Ethernet Mac addresses

Layer 3 (Network): IP addresses

Layer 4 (Transport): TCP port numbers