Catatan Penting
Saya tidak akan memberitahukan detail proses reverse engineering Brontok, karena sepertinya pembuat brontok sangat memperhatikan semua hal yang tertulis di Internet untuk memperbaiki virusnya. Misalnya ketika dia mengetahui bahwa kompresor Mew dapat dibongkar dengan UnMew, maka pembuatnya segera mengganti dengan kompresor lain. Setelah mengetahui bahwa programnya dapat dengan mudah dibunuh dengan KillVB, atau dengan merename MSVBVM60.DLL (dari mode DOS), maka dia mengganti bahasa yang dipakainya menjadi Visual C++.
Pembuat virus yang sangat rajin
Saya telah mengkritik banyak hal mengenai brontok dalam tulisan saya sebelumnya. Sekarang pembuat virus sudah memperbaikinya. Perbaikan yang dilakukannya adalah sebagai berikut:
1. Virus sekarang ditulis menggunakan Visual C++, sehingga tidak bisa lagi dibunuh menggunakan KILLVB ( Sesuai namanya, KillVB hanya membunuh proses Visual Basic). Ini juga berarti bahwa mengubah atau menghapus file MSVBVM60.DLL tidak lagi bisa menghentikan Brontok.
2. Virus mengganti nama %systemroot%\system32\MSVBVM60.DLL menjadi nama lain (msvbvm60.dll.
3. Pesan email yang dikirim virus sekarang ditulis dalam bahasa Inggris dan Indonesia, namun pesan yang dibuat dalam file teks tetap berbahasa Indonesia.
4. Virus tidak lagi merestart komputer, tapi menutup aplikasi dengan judul window tertentu.
5. Virus tidak lagi memiliki MD5 yang tetap meskipun memiliki ukuran yang tetap, sehingga program penghapus yang berbasis MD5 tidak akan bekerja dengan benar. Brontok mengubah dirinya sendiri ketika diaktifkan. Perubahan dilakukan terhadap nama section pada portable executable header.
6. Dulu isi mail dan attachment didownload dari Internet, sekarang isi attachment ada pada brontok. Brontok akan mengirimkan sebuah file ZIP bernama Photos.zip di dalamnya terdapat file Photo.bmp (ini sebenarnya file executable), dan file View Photo.bat. Jika Anda mengklik file Photo.bmp maka tidak akan terjadi apa-apa, tapi jika Anda mengklik file View Photo.bat, file Photo.bmp akan dijalankan. Untuk menutupi aksinya, program Photo.bmp akan berpura-pura menjalankan program mspaint.exe.
7. Program Photo.bmp adalah downloader yang akan mendownload file executable dari Internet dan menjalankan file yang didownload tersebut (isi filenya bisa apa saja).
8. Brontok menambahkan beberapa key registry, dan makin banyak menggunakan nama file dan nama key registry yang acak.
9. Brontok tidak lagi melakukan DDOS terhadap situs-situs tertentu. Hal ini merupakan hal yang baik karena Brontok memakan bandwidth sangat banyak. Sebagai gantinya, brontok sekarang memblok akses ke berbagai situs dengan memodifikasi file HOSTS. (Situs compactbyte.com merupakan salah satu situs yang diblok)
Perkembangan kemampuan pembuat virus brontok
Kemampuan pembuat virus ini cukup berkembang. Program dalam bahasa C yang dibuatnya sudah lumayan baik untuk seorang pemula, namun tidak menunjukkan adanya penggunaan teknik tingkat lanjut (misalnya pembuat virus ini kurang memanfaatkan fungsi sprintf dalam manipulasi stringnya). Pembuatan program dalam bahasa C ini masih suatu terjemahan langsung dari source code dalam VB dan belum dioptimasi dengan baik.
Pembersihan
Gunakan CompactbyteAV atau antivirus lain. Saya tidak lagi memberikan langkah pembersihan mendetail karena banyak orang awam yang masih bingung dengan langkah yang saya berikan dan banyak yang menanyakan langkah yang lebih detail lagi. Ukuran file CompactbyteAV kurang dari 50kb (versi saat ini sekitar 35kb), sehingga dapat dengan mudah Anda simpan di USB Disk.
Senin, 16 Maret 2009
Brontok Versi Baru
apa itu komputer
Definisi
Komputer berasal dari bahasa latin computare yang mengandung arti menghitung. Karena luasnya bidang garapan ilmu komputer, para pakar dan peneliti sedikit berbeda dalam mendefinisikan termininologi komputer.
• Menurut Hamacher [1], komputer adalah mesin penghitung elektronik yang cepat dan dapat menerima informasi input digital, kemudian memprosesnya sesuai dengan program yang tersimpan di memorinya, dan menghasilkan output berupa informasi.
• Menurut Blissmer [2], komputer adalah suatu alat elektonik yang mampu melakukan beberapa tugas sebagai berikut:
- menerima input
- memproses input tadi sesuai dengan programnya
- menyimpan perintah-perintah dan hasil dari pengolahan
- menyediakan output dalam bentuk informasi
• Sedangan Fuori [3] berpendapat bahwa komputer adalah suatu pemroses data yang dapat melakukan perhitungan besar secara cepat, termasuk perhitungan aritmetika dan operasi logika, tanpa campur tangan dari manusia.
Untuk mewujudkan konsepsi komputer sebagai pengolah data untuk menghasilkan suatu informasi, maka diperlukan sistem komputer (computer system) yang elemennya terdiri dari hardware, software dan brainware. Ketiga elemen sistem komputer tersebut harus saling berhubungan dan membentuk kesatuan. Hardware tidak akan berfungsi apabila tanpa software, demikian juga sebaliknya. Dan keduanya tiada bermanfaat apabila tidak ada manusia (brainware) yang mengoperasikan dan mengendalikannya.
1. Hardware atau Perangkat Keras: peralatan yang secara fisik terlihat dan bisa djamah.
2. Software atau Perangkat Lunak: program yang berisi instruksi/perintah untuk melakukan pengolahan data.
3. Brainware: manusia yang mengoperasikan dan mengendalikan sistem komputer.
Penggolongan Komputer
Literatur terbaru tentang komputer melakukan penggolongan komputer berdasarkan tigal hal: data yang diolah, penggunaan, kapasitas/ukurannya, dan generasinya.
Berdasarkan Data Yang Diolah
1. Komputer Analog
2. Komputer Digital
3. Komputer Hybrid
Berdasarkan Penggunannya
1. Komputer Untuk Tujuan Khusus (Special Purpose Computer)
2. Komputer Untuk Tujuan Umum (General Purpose Computer)
Berdasarkan Kapasitas dan Ukurannya
1. Komputer Mikro (Micro Computer)
2. Komputer Mini (Mini Computer)
3. Komputer Kecil (Small Computer)
4. Komputer Menengah (Medium Computer)
5. Komputer Besar (Large Computer)
6. Komputer Super (Super Computer)
Berdasarkan Generasinya
1. Komputer Generasi Pertama (1946-1959)
2. Komputer Generasi Kedua (1959-1964)
3. Komputer Generasi Ketiga (1964-1970)
4. Komputer Generasi Keempat (1979-sekarang)
5. Komputer Generasi Kelima
joomla
Apa itu Joomla?
Joomla adalah Open Sorce CMS.
Apa itu CMS?
CMS adalah singkatan dari Content Management System.
Apa itu Content Management System?
Content Management System adalah Sebuah sistem yang digunakan untuk mengatur isi website dengan baik dan mudah.
Mengapa disebut Open Source?
Software/aplikasi web Joomla, terdiri dari kode-kode hasil karya programer-programer hebat dari penjuru dunia. Umumnya kode itu dijual, dan tidak murah. Inilah yang menjelaskan mengapa windows bajakan kamu tiba-tiba menjadi haram! Karena kamu harus membeli kode-kode itu, dul!
Open Source, adalah upaya untuk melepaskan kode-kode program kepada publik. Publik (yang mengerti) mengolahnya kembali menjadi lebih baik dan mudah diterima masyarakat (user friendly). Dan hasil yang sudah baik itu, diberikan secara cuma-cuma kepada masarakat.
Mengapa harus Content Management System?
Tidak harus man! Kata siapa harus? Content Management System dipakai karena keluwesannya mengatur isi website.
Apa maksudnya luwes?
Maksudnya adalah amat mudah diperbaharui dan dinamis. Kalau isi website kamu tadinya sedikit, lalu pada suatu hari tiba-tiba menyadari bahwa website kamu semakin berkembang dan banyak pengunjungnya. Maka kamu perlu website yang mudah dihandle. CMS Joomla adalah salah satu jawabannya.
Apa saja isinya Joomla?
Kalau kamu Blogger, maka kamu tahu, apa isi blog kamu. Nah, Joomla itu lebih lengkap daripada sekedar WebBlog. Kalau kamu bukan Blogger, dan mau membuat website, entah itu untuk dagang, untuk sekolah, untuk komunitas/organisasi, maka Joomla adalah salah satu aplikasi web yang baik dan mudah dipelajari.
Kenapa baik dan mudah?
Karena gratis dan gampang installnya. Selain itu, didukung oleh komunitas internasional yang banyak. Lebih hebat lagi, berbahasa Indonesia loh.
Saya newbie… ralat, saya dummies. Gimana dong?
Pengguna Joomla itu biasanya terbagi dalam tingkatan user.
- Ada Basic User, yang bisanya cuman nginstal dan pakai… kalau bosan, uninstall.
- Ada Advance User, yang udah bisa ngutak-ngatik dikit script PHP, XML, MySql.
- Ada lagi Jagowan User. Yang mengembangkan sistem ini. Mereka adalah perancang, pembuat, pengeksekusi, penangkal serangan musuh, pengaman sistem, pengembang serta pembuat template dan sebagainya. Selain hebat, mereka juga orang-orang yang murah hati. Mereka bekerja gratis, bo! Murni sukarelawan tanpa pamrih. Bahkan ada yang rela nama aseli nya nggak disebut. Bener-bener Hamba Allah yang tidak mau disebutkan nama aslinya (walopun tetap harus pakai nama nick di cyberworld, karena itu kewajiban etik jagowan).
Selain tiga kategori diatas, terdapat pula kategori temen-temennya jagowan, yaitu yang membantu jagowan mengembangkan sistem ini, mereka disebut 3rd party developer. Mereka ada yang volunteer, alias pekerja gratis…, adapula Soldier of Fortune, alias prajurit bayaran, menarik bayaran dari user yang mendownload program mereka. Semuanya sah-sah saja. Sebab biasanya harga 3rd party juga ga mahal-mahal amat kok.
distro linux
Distro Linux (singkatan dari distribusi Linux) adalah sebutan untuk sistem operasi komputer dan aplikasinya, merupakan keluarga Unix yang menggunakan kernel Linux. Distribusi Linux bisa berupa perangkat lunak bebas dan bisa juga berupa perangkat lunak komersial seperti Red Hat Enterprise, SuSE, dan lain-lain.
Ada banyak distribusi atau distro Linux yang telah muncul. Beberapa bertahan dan besar, bahkan sampai menghasilkan distro turunan, contohnya adalah Distro Debian GNU/Linux. Distro ini telah menghasilkan puluhan distro anak, antara lain Ubuntu, Knoppix, Xandros, DSL, dan sebagainya.
Untuk mendapatkan distro linux, anda dapat mendownloadnya langsung dari situs distributor distro bersangkutan, atau membelinya dari penjual lokal.
•
CD Linux
CD Linux (maksudnya CD Distro Linux atau CD Sistem Operasi dan aplikasi Linux) adalah istilah yang sering digunakan untuk menyebut CD distribusi Linux secara umum.
CD Linux biasanya didapatkan dengan mem-burn/menulis sebuah berkas ISO distro Linux ke CD kosong. CD Linux dapat anda dapatkan gratis ataupun berbayar.
Daftar distribusi Linux
Distribusi-distribusi Linux dapat dikategorikan berdasarkan sistem manajemen paket, bebas dan tidak, tujuan pembuatan, perangkat lunak dasar yang digunakan, dan lain sebagainya.
Distribusi bebas berbasis Debian
• 64Studio
• Adamantix
• Amber Linux
• BeatrIX
• Bonzai Linux
• Debian
• Debian-BR-CDD
• DeveLinux
• Elive
• Finnix
• GenieOS
• Gnoppix
• Guadalinex
• Hiweed
• Kalango
• Kanotix
• Knoppix
• Kuliax (sebuah distro Linux yang dikembangkan Indonesia)
• Kurumin
• LinEx
• Loco Linux
• MeNTOPPIX
• Morphix
• NepaLinux
• PingOO
• Skolelinux
• Sun Wah RAYS LX
• Symphony OS
• Ubuntu
o BlankOn Linux (sebuah distro Linux yang dikembangkan Indonesia)
o Dewalinux (sebuah distro Linux yang dikembangkan Indonesia)
o Briker (sebuah distro Linux yang dikembangkan Indonesia)
o Edubuntu
o Kubuntu
o Xubuntu
o De2
• Xandros
• Zen Linux
Distribusi berbasiskan RPM
• aLinux
• ALT Linux
• Annvix
• Ark Linux
• ASPLinux
• Aurox
• Berry Linux
• BLAG Linux and GNU
• BlankOn versi pertama (sebuah distro Linux yang dikembangkan Indonesia)
• Caixa Mágica
• cAos Linux
• CentOS
• Cobind
• Conectiva
• EduLinux
• Engarde Secure Linux
• Fox Linux
• IGOS Nusantara (sebuah distro linux yang dikembangkan Indonesia)
• Linux Mobile System
• Magic Linux
• Mandriva Linux (dahulu bernama Mandrake Linux)
• NOPPENLINUX
• PCLinuxOS
• PCQLinux2005
• PLD Linux Distribution
• QiLinux
• Red Hat Linux:
o Fedora Core
o Red Flag Linux
o Scientific Linux
o Vine Linux
o White Box Enterprise Linux
o Yellow Dog Linux
• Sesco Linux: A secure Linux distribution, solely recompiled from the source distributed under GPL by Sesco information Systems Inc., (in RPM-based distributions).
• SUSE Linux
• Tinfoil Hat Linux
• Trustix
• Ulteo
• YOPER ("Your Operating System")
Distribusi bebas berbasis Slackware
• AliXe
• Austrumi
• BackTrack
• Bluewhite64 Linux
• CD Forum Linux (sebuah distro Linux yang dikembangkan Indonesia)
• College Linux
• Cytrun Linux
• DARKSTAR
• DeepStyle
• easys GNU/Linux
• Frugalware
• Hardened Linux
• Kate OS
• MooLux
• Plamo Linux
• SLAX
• Sauver
• Singkong Linux (sebuah distro Linux yang dikembangkan Indonesia)
• Slackintosh
• Slackware
• Slamd64
• Splack Linux
• targeT Linux (sebuah distro Linux yang dikembangkan Indonesia)
• TopologiLinux
• Truva Linux
• Ultima Linux
• Vector Linux
• Wolvix
• 0x7F GNU/Linux
• ZenCafe Linux (sebuah distro Linux yang dikembangkan Indonesia)
• Zenwalk Linux (dulu MiniSlack)
Distribusi bebas berbasis lainnya
Distribusi-distribusi Linux berikut ini memakai sistem manajemen paket sendiri, gabungan atau tidak sama sekali
• Arch Linux (dengan sistem manajemen paket Pacman)
• Coyote Linux (distro Router/firewall)
• CRUX (menggunakan manajemen paket berbasis tar.gz yang sederhana, BSD-style initscripts)
• DD-WRT (embedded firewall)
• DeLi Linux (kombinasi Slackware dan CRUX)
• Devil-Linux (distro firewall/router/server)
• DSLinux (Linux untuk Nintendo DS)
• dyne:bolic (instalasi software baru cukup dengan menyalin [copy] ke direktori tertentu)
• Familiar Linux (distro untuk iPAQ handhelds)
• Fli4l (distro yang muat dalam satu floppy disk)
• Foresight Linux (menggunakan sistem manajemen paket Conary)
• FREESCO (router)
• GeeXboX (media center)
• GoboLinux (manajemen paket sendiri yang menggunakan symlink)
• Hikarunix (distro khusus untuk main Go)
• IPCop (distro Router/firewall)
• iPodLinux (linux untuk Apple iPod berbasis µCLinux kernel)
• Jlime (distro untuk HP Jornada 6xx dan 7xx dan NEC MobilePro 900(c) handhelds)
• Lunar Linux (distro berbasis source code)
• MCC Interim Linux (mungkin ini distro Linux pertama; dibuat oleh Manchester Computing Centre di bulan February 1992)
• MkLinux distro untuk PowerPC, menjalankan Linux kernel sebagai server di atas Mach microkernel)
• Mobilinux (buatan Montavista untuk smartphones)
• MontaVista Linux (embedded systems distro buatan MontaVista Software)
• NASLite (distro floppy-disk untuk menjalankan perangkat Network Attached Storage / NAS)
• Nitix (autonomic server buatan Net Integration Technologies Inc.)
• OpenWrt (embedded firewall)
• Pardus (buatan Turki; menggunakan sistem manajemen paket PISI, dan COMAR configuration framework)
• PS2 Linux (distro Sony Computer Entertainment unuk PlayStation 2 video game console)
• Puppy Linux (sistem manajemen paket PetGet dan DotPup; tapi mulai versi 3 juga bisa menggunakan paket Slackware)
• Rocks Cluster Distribution (untuk computer cluster = gabungan beberapa komputer menjadi satu super komputer)
• rPath (menggunakan sistem manajemen paket Conary)
• Sentry Firewall (firewall, server sistem)
• SliTaz GNU/Linux
• Smallfoot
• SmoothWall (router/firewall)
• Softlanding Linux System (salah satu distro tertua, dibangun tahun 1992-1994; basis awal Slackware)
• Sorcerer (berbasis source code)
• Source Mage GNU/Linux (berbasis source code)
• Tinfoil Hat Linux (distro floppy-disk)
• tomsrtbt (root boot disk)
Wireless
Wireless
Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires".[1] The distances involved may be short (a few meters as in television remote control) or long (thousands or millions of kilometers for radio communications). When the context is clear, the term is often shortened to "wireless". Wireless communication is generally considered to be a branch of telecommunications.
It encompasses various types of fixed, mobile, and portable two way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice, keyboards and headsets, satellite television and cordless telephones.
Introduction
Handheld wireless radios such as this Maritime VHF radio transceiver use electromagnetic waves to implement a form of wireless communications technology.
Wireless operations permits services, such as long range communications, that are impossible or impractical to implement with the use of wires. The term is commonly used in the telecommunications industry to refer to telecommunications systems (e.g., radio transmitters and receivers, remote controls, computer networks, network terminals, etc.) which use some form of energy (e.g. radio frequency (RF), infrared light, laser light, visible light, acoustic energy, etc.) to transfer information without the use of wires.[2] Information is transferred in this manner over both short and long distances.
Wireless communication
The term "wireless" has become a generic and all-encompassing word used to describe communications in which electromagnetic waves or RF (rather than some form of wire) carry a signal over part or the entire communication path. Common examples of wireless equipment in use today include:
• Professional LMR (Land Mobile Radio) and SMR (Specialized Mobile Radio) typically used by business, industrial and Public Safety entities
• Consumer Two Way Radio including FRS (Family Radio Service), GMRS (General Mobile Radio Service) and Citizens band ("CB") radios
• The Amateur Radio Service (Ham radio)
• Consumer and professional Marine VHF radios
• Cellular telephones and pagers: provide connectivity for portable and mobile applications, both personal and business.
• Global Positioning System (GPS): allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth.
• Cordless computer peripherals: the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless.
• Cordless telephone sets: these are limited-range devices, not to be confused with cell phones.
• Satellite television: allows viewers in almost any location to select from hundreds of channels.
• Wireless gaming: new gaming consoles allow players to interact and play in the same game regardless of whether they are playing on different consoles. Players can chat, send text messages as well as record sound and send it to their friends. Controllers also use wireless technology. They do not have any cords but they can send the information from what is being pressed on the controller to the main console which then processes this information and makes it happen in the game. All of these steps are completed in milliseconds.
Wireless networking (i.e. the various types of unlicensed 2.4 GHz WiFi devices) is used to meet many needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology:
• To span a distance beyond the capabilities of typical cabling,
• To avoid obstacles such as physical structures, EMI, or RFI,
• To provide a backup communications link in case of normal network failure,
• To link portable or temporary workstations,
• To overcome situations where normal cabling is difficult or financially impractical, or
• To remotely connect mobile users or networks.
Wireless communication can be via:
• radio frequency communication,
• microwave communication, for example long-range line-of-sight via highly directional antennas, or short-range communication, or
• infrared (IR) short-range communication, for example from remote controls or via IRDA.
Applications may involve point-to-point communication, point-to-multipoint communication, broadcasting, cellular networks and other wireless networks.
The term "wireless" should not be confused with the term "cordless", which is generally used to refer to powered electrical or electronic devices that are able to operate from a portable power source (e.g. a battery pack) without any cable or cord to limit the mobility of the cordless device through a connection to the mains power supply. Some cordless devices, such as cordless telephones, are also wireless in the sense that information is transferred from the cordless telephone to the telephone's base unit via some type of wireless communications link. This has caused some disparity in the usage of the term "cordless", for example in Digital Enhanced Cordless Telecommunications.
In the last fifty years, wireless communications industry experienced drastic changes driven by many technology innovations.
History
Main article: History of radio
The term "Wireless" came into public use to refer to a radio receiver or transceiver (a dual purpose receiver and transmitter device), establishing its usage in the field of wireless telegraphy early on; now the term is used to describe modern wireless connections such as in cellular networks and wireless broadband Internet. It is also used in a general sense to refer to any type of operation that is implemented without the use of wires, such as "wireless remote control" or "wireless energy transfer", regardless of the specific technology (e.g. radio, infrared, ultrasonic) that is used to accomplish the operation.
Early wireless work
David E. Hughes, eight years before Hertz's experiments, induced electromagnetic waves in a signaling system. Hughes transmitted Morse code by an induction apparatus. In 1878, Hughes's induction transmission method utilized a "clockwork transmitter" to transmit signals. In 1885, T. A. Edison used a vibrator magnet for induction transmission. In 1888, Edison deploys a system of signaling on the Lehigh Valley Railroad. In 1891, Edison attains the wireless patent for this method using inductance (U.S. Patent 465,971 ).
In the history of wireless technology, the demonstration of the theory of electromagnetic waves by Heinrich Rudolf Hertz in 1888 was important.[3][4] The theory of electromagnetic waves were predicted from the research of James Clerk Maxwell and Michael Faraday. Hertz demonstrated that electromagnetic waves could be transmitted and caused to travel through space at straight lines and that they were able to be received by an experimental apparatus.[3][4] The experiments were not followed up by Hertz. The practical applications of the wireless communication and remote control technology were implemented by Nikola Tesla.
Further information: Invention of radio
The electromagnetic spectrum
Light, colours, AM and FM radio, and electronic devices make use of the electromagnetic spectrum. In the US the frequencies that are available for use for communication are treated as a public resource and are regulated by the Federal Communications Commission. This determines which frequency ranges can be used for what purpose and by whom. In the absence of such control or alternative arrangements such as a privatized electromagnetic spectrum, chaos might result if, for example, airlines didn't have specific frequencies to work under and an amateur radio operator was interfering with the pilot's ability to land an airplane. Wireless communication spans the spectrum from 9 kHz to 300 GHz. (Also see Spectrum management)
Applications of wireless technology
Security systems
Wireless technology may supplement or replace hard wired implementations in security systems for homes or office buildings
Television remote control
Modern televisions use wireless (generally infrared) remote control units. Now radio waves are also used.
Cellular telephony (phones and modems)
Perhaps the best known example of wireless technology is the cellular telephone and modems. These instruments use radio waves to enable the operator to make phone calls from many locations world-wide. They can be used anywhere that there is a cellular telephone site to house the equipment that is required to transmit and receive the signal that is used to transfer both voice and data to and from these instruments.
WiFi
Main article: Wi-Fi
Wi-Fi (for wireless fidelity) is a wireless LAN technology that enables laptop PC’s, PDA’s, and other devices to connect easily to the internet. Technically known as IEEE 802.11b, Wi-Fi is faster and less expensive than standard Ethernet and other common wire-based LAN technologies. Several Wi-Fi hot spots have been popular over the past few years. Some businesses charge customers a monthly fee for service, while others have begun offering it for free in an effort to increase the sales of their goods.[5]
Wireless energy transfer
Main article: Wireless energy transfer
Wireless energy transfer is a process whereby electrical energy is transmitted from a power source to an electrical load that does not have a built-in power source, without the use of interconnecting wires.
Categories of wireless implementations, devices and standards
• Radio communication system
• Broadcasting
• Amateur radio
• Land Mobile Radio or Professional Mobile Radio: TETRA, P25, OpenSky, EDACS, DMR, dPMR
• Communication radio
• Cordless telephony:DECT (Digital Enhanced Cordless Telecommunications)
• Cellular systems: 0G, 1G, 2G, 3G, Beyond 3G (4G), Future wireless
• List of emerging technologies
• Short-range point-to-point communication : Wireless microphones, Remote controls, IrDA, RFID (Radio Frequency Identification), Wireless USB, DSRC (Dedicated Short Range Communications), EnOcean, Near Field Communication
• Wireless sensor networks: ZigBee, EnOcean; Personal area networks, Bluetooth, TransferJet, Ultra-wideband (UWB from WiMedia Alliance).
• Wireless computer networks: Wireless Local Area Networks (WLAN), (IEEE 802.11 branded as WiFi and HiperLAN), Wireless Metropolitan Area Networks (WMAN) and Broadband Fixed Access (BWA) (LMDS, WiMAX, WANKA and HiperMAN)
Computer network
Computer network
.
A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network.
Introduction
A network is a collection of computers and devices connected to each other. The network allows computers to communicate with each other and share resources and information. The Advance Research Projects Agency (ARPA) designed "Advanced Research Projects Agency Network" (ARPANET) for the United States Department of Defense. It was the first computer network in the world in late 1960's and early 1970's.[1]
Network classification
The following list presents categories used for classifying networks.
Connection method
Computer networks can also be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as Optical fiber, Ethernet, Wireless LAN, HomePNA, Power line communication or G.hn.
Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges and/or routers.
Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium.
ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network.
Scale
Based on their scale, networks can be classified as Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Network (MAN), Personal Area Network (PAN), Virtual Private Network (VPN), Campus Area Network (CAN), Storage Area Network (SAN), etc.
Functional relationship (network architecture)
Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., Active Networking, Client-server and Peer-to-peer (workgroup) architecture.
[edit] Network topology
Main article: Network topology
Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network, star-bus network, tree or hierarchical topology network. Network topology signifies the way in which devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks.
Types of networks
Below is a list of the most common types of computer networks in order of scale.
[edit] Personal area network
Main article: Personal area network
A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that are used in a PAN are printers, fax machines, telephones, PDAs and scanners. The reach of a PAN is typically about 20-30 feet (approximately 6-9 meters), but this is expected to increase with technology improvements.
Local area network
Main article: Local area network
A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. Current wired LANs are most likely to be based on Ethernet technology, although new standards like ITU-T G.hn also provide a way to create a wired LAN using existing home wires (coaxial cables, phone lines and power lines)[2].
For example, a library may have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet. On a wired LAN, PCs in the library are typically connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnected devices and eventually connect to the Internet. The cables to the servers are typically on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbit/s. A wireless LAN may exist using a different IEEE protocol, 802.11b, 802.11g or possibly 802.11n. The staff computers (bright green in the figure) can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup.
Typical library network, in a branching tree topology and controlled access to resources
All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers.
The defining characteristics of LANs, in contrast to WANs (wide area networks), include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 100 Gbit/s, and possibly 400 Gbit/s.
Campus area network
Main article: Campus area network
A campus area network (CAN) is a computer network made up of an interconnection of local area networks (LANs) within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting.
In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network (WAN) (in some cases).
The main aim of a campus area network is to facilitate students accessing internet and university resources. This is a network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, office building, or a military base. A CAN may be considered a type of MAN (metropolitan area network), but is generally limited to a smaller area than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area. This should not be confused with a Controller Area Network. A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet.
Metropolitan area network
Main article: Metropolitan area network
A metropolitan area network (MAN) is a network that connects two or more local area networks or campus area networks together but does not extend beyond the boundaries of the immediate town/city. Routers, switches and hubs are connected to create a metropolitan area network.
Wide area network
Main article: Wide Area Network
A wide area network (WAN) is a computer network that covers a broad area (i.e. any network whose communications links cross metropolitan, regional, or national boundaries [1]). Less formally, a WAN is a network that uses routers and public communications links [1]. Contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs), which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively. The largest and most well-known example of a WAN is the Internet. A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.
Global area network
Main article: IEEE 802.20
A global area networks (GAN) specification is in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is "handing off" the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial WIRELESS local area networks (WLAN).[3]
Virtual private network
Main article: Virtual Private Network
A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The link-layer protocols of the virtual network are said to be tunneled through the larger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.
A VPN may have best-effort performance, or may have a defined service level agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point.
A VPN allows computer users to appear to be editing from an IP address location other than the one which connects the actual computer to the Internet.
Internetwork
Main article: Internetwork
Internetworking involves connecting two or more distinct computer networks or network segments via a common routing technology. The result is called an internetwork (often shortened to internet). Two or more networks or network segments connected using devices that operate at layer 3 (the 'network' layer) of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.
In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them:
• Intranet
• Extranet
• Internet
Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.
Intranet
Main article: Intranet
An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.
Extranet
Main article: Extranet
An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities (e.g., a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint). Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
Internet
Main article: Internet
The Internet is a specific internetwork. It consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol Suite. It is the successor of the Advanced Research Projects Agency Network (ARPANET) developed by DARPA of the U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web (WWW). The 'Internet' is most commonly spelled with a capital 'I' as a proper noun, for historical reasons and to distinguish it from other generic internetworks.
Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing system (IP Addresses) administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol (BGP), forming a redundant worldwide mesh of transmission paths.
Basic hardware components
All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In addition, some method of connecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). Less common are microwave links (as in IEEE 802.12) or optical cable ("optical fiber"). An ethernet card may also be required.
Network interface cards
Main article: Network card
A network card, network adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC addresses.
Repeaters
Main article: Repeater
A repeater is an electronic device that receives a signal and retransmits it at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable which runs longer than 100 meters.
Hubs
Main article: Network hub
A hub contains multiple ports. When a packet arrives at one port, it is copied unmodified to all ports of the hub for transmission. The destination address in the frame is not changed to a broadcast address.[4]
Bridges
Main article: Network bridge
A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received.
Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived.
Bridges come in three basic types:
1. Local bridges: Directly connect local area networks (LANs)
2. Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced by routers.
3. Wireless bridges: Can be used to join LANs or connect remote stations to LANs.
Switches
Main article: Network switch
A switch is a device that forwards and filters OSI layer 2 datagrams (chunk of data communication) between ports (connected cables) based on the MAC addresses in the packets.[5] This is distinct from a hub in that it only forwards the packets to the ports involved in the communications rather than all ports connected. Strictly speaking, a switch is not capable of routing traffic based on IP address (OSI Layer 3) which is necessary for communicating between network segments or within a large or complex LAN. Some switches are capable of routing based on IP addresses but are still called switches as a marketing term. A switch normally has numerous ports, with the intention being that most or all of the network is connected directly to the switch, or another switch that is in turn connected to a switch.[6]
Switch is a marketing term that encompasses routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). Switches may operate at one or more OSI model layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch.
Overemphasizing the ill-defined term "switch" often leads to confusion when first trying to understand networking. Many experienced network designers and operators recommend starting with the logic of devices dealing with only one protocol level, not all of which are covered by OSI. Multilayer device selection is an advanced topic that may lead to selecting particular implementations, but multilayer switching is simply not a real-world design concept.
hacker
Computing and technology
• Hacker (computer security), someone involved in computer security/insecurity[1]
• Hacker (programmer subculture), a programmer subculture originating in the US academia in the 1960s, which is nowadays mainly notable for the free software/open source movement
• Hacker (hobbyist), an enthusiastic home computer hobbyist
See Hacker (computing) for an overview of different kinds of computer hackers and the relationships between these groups.
Similar meanings in other fields are:
• Mathematics hacker, a type of reality hacker (or hacker of numbers beyond reals), but focused on math--quite likely also in a computer science (or other) context
• Media hacker, someone who uses the media in new ways
• Reality hacker, similar to a computer hacker, but hacks the "real world"
• Wetware hacker, one who experiments with biological materials
Entertainment
• Hackers: Heroes of the Computer Revolution, a 1984 book by Steven Levy.
• Hacker (computer game), a 1985 computer game by Activision
• Hacker (card game), a 1992 publication of Steve Jackson Games
• Hackers (film), a 1995 film
People named Hacker
Real
• Alan Ray Hacker (b. 1938), English clarinetist
• Benjamin Thurman Hacker (1935-2003), U.S. Naval officer
• George Hacker (20th century), U.S. lawyer, head of the Alcohol Policies Project
• Marilyn Hacker (b. 1942), American poet, critic, and reviewer
• Peter Hacker (b. 1939), British philosopher
• Sally Hacker (1936–1988), feminist sociologist
• The Hacker (Michel Amato, b. 1972), French electroclash and techno producer
Fictional
• J. Random Hacker, the mythical/archetypal hacker nerd
• Hacker, a character of the TV series Cyberchase (see List of Cyberchase characters#Hacker)
• Sgt. Charley Hacker, a character on the TV series Gomer Pyle, U.S.M.C. (see List of The Gomer Pyle, U.S.M.C. Characters#Staff Sergeant Hacker)
• Hacker, the cyborg sidekick character in The Centurions (TV series)
• Jim Hacker, the principal character in Yes Minister
Other definitions
New York street sign, c. 1963
• Hacker (folklore), a mythological race in Scandinavian folklore
• A mediocre golfer[2]
• Someone who practices casual equestrianism, in particular trail riding
• A person skilled in the creation of a hack (masonry)[3]
• A musician who plays out of turn or shows off constantly
• A player of NetHack, and other rogue-like games
• A taxicab driver (from the shortened form of hackney carriage).
• A brewery which merged with Pschorr in 1972, now the Hacker-Pschorr Brewery, and the beer it produces.
• A basketball player who has limited defensive ability and is prone to fouling.
