nyuuzyou/kompy huggingface dataset:
ISO / OSI Model darajasi funktsiyalari

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ISO / OSI Model darajasi funktsiyalari
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bet | 3/8 | Sana | 27.05.2024 | Hajmi | 0,66 Mb. | | #255230 |
Bog'liq KAMPYUTER TARMOQLARI REF
ISO / OSI Model darajasi funktsiyalari
Jismoniy darajasi . Ushbu qatlam bitlarni jismoniy kanallar orqali uzatish bilan shug'ullanadi, masalan, koaksiyal kabel, burilgan juft kabel yoki optik tolali kabel. Ma'lumot uzatishning jismoniy muhitining xususiyatlari, masalan, o'tkazish qobiliyati, shovqin immuniteti, empedans va boshqalar, bu darajaga bog'liq. Xuddi shu darajada, elektr signallarining xarakteristikalari aniqlanadi, masalan, pulslarning chekkalari, uzatiladigan signalning kuchlanishi yoki oqim darajasi, kodlash turi, signal uzatish tezligi. Bunga qo'shimcha ravishda, ulagich turlari va har bir pinning maqsadi bu erda standartlashtirilgan.
Jismoniy qatlam funktsiyalari tarmoqqa ulangan barcha qurilmalarda amalga oshiriladi. Kompyuter tomonida fizik qatlam funktsiyalari tarmoq adapteri yoki ketma-ket port orqali amalga oshiriladi.
1-Sath:Ushbu qatlam fizik rozetkalar va rozetkalar va faqat signallarning elektr xususiyatlari bilan shug'ullanadi.
2-sath:Ma'lumotlar havolasi sathi fizik sathdan freymlarga bo'laklarga bo'linadi (ma'lumotlar uchun mantiqiy, tuzilgan paketlar). ITU-T Rec-da ko'rsatilgan. X.212 [ISO / IEC 8886] , ITU-T Rec. X.222 va boshqalar. Ushbu qatlam freymlarni bitta xostdan boshqasiga o'tkazish uchun javobgardir. Xatolarni tekshirishni amalga oshirishi mumkin. Ushbu qatlam keyinchalik ikkita sublayerdan iborat: MAC va LLC .
3-sath:Ulanishsiz tarmoq xizmati (CLNS) - ITU-T Rec. X.213 [ISO / IEC 8348] . SCCP X.213-ga asoslangan. Ulanishsiz tarmoq protokoli (CLNP) - ITU-T Rec. X.233 [ISO / IEC 8473- 1] . Ulanish-yo'naltirilgan tarmoq xizmati (CONS) - ITU-T Rec. X.213 [ISO / IEC 8348] . Ulanish-yo'naltirilgan tarmoq protokoli ( X.25 ) - ITU-T Rec. X.233 [ISO / IEC 8878] . Bu X.25 protokolidan CONSni ta'minlash uchun foydalanish.
4-sath:Ulanish rejimida va ulanmasdan rejimda transport xizmatlari ITU-T Rec tomonidan belgilanadi . X.214 [ISO / IEC 8072] ; ulanish rejimi xizmatini ta'minlovchi protokol ITU-T Rec tomonidan belgilanadi . X.224 [ISO / IEC 8073] va ulanishsiz rejimda xizmat ko'rsatishni ta'minlovchi protokoli ITUT Recr tomonidan belgilanadi . X.234 [ISO / IEC 8602] .
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Optik kuchaytirgichlarning qiyosiy tafsivi

aktiv muhit sifatida tolali yorug'lik uzatkichining o‘zidan foydalanish imkoniyatining mavjudligi;
tayyorlash texnologiyasining yaxshi o'zlashtirilganligi;
kuchaytirish koeffltsiyentining kattaligi;
shovqin koeffitsiyentining nisbatan kamligi
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istalgan to'lqin uzun- ligida ishlash imkoniyati;
aktiv muhit sifatida tolali yorug'likuzatki- chining o‘zidan foydalanish imkoniyatining mavjudligi;
tegishli to'lqin uzun- likli damlash manbayi - lazer diodini tanlab olish yo‘li bilan kuchaytirish jarayonini bir necha 10 nmli oraliqda shakllantirish mumkin- Hgi;
past sathli shovqinga ega ekanligi
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o'lchamlari va massasi- ning kichikligi;
elektr energiyasini bevosita yorug'lik energiyasiga aylantirib berishga asoslanganligi;
iste’mol quvvatining kamligi;
optik tolaning barcha shaffoflik «darcha»larida bir xil samaradorlikbilan ishlash xususiyati;
boshqa elementlar, masalan, lazer diodi bilan birgalikda
yaxlit (integral) ko'rinishda tayyorlash imkoniyatining mavjudligi
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Aralashmali tolali optik kuchaytir­gichlar

Aralashmali tolali optik kuchaytirgichlar
Optik aloqa asoslari (N.Yusupov, R.Isayev)
176 www.ziyouz.com kutubxonasi Optik kuchaytirgichlarning parametrlarini aniqlash va hisoblash usullari Optik kuchaytirgichlar quyidagi parametrlar bilan tavsiflanadi. Kuchaytirish koefiitsenti. Bu parametr chiqish signalining quwati kirish signalining quwatiga nisbatan necha marta katta ekanligini ko‘rsatadi. G=Ph I Л (5.4) bunda Pchiq va Air - mos ravishda kuchaytirgichning kirishidagi va chiqishidagi nurlanish signali quwati. Logarifmik ko‘rinishda bu kattalik g=lgG (5.5) munosabat bilan aniqlanadi. Kuchaytirish koeffitsiyentining kattaligi, avval ta’kidlab o'tilganidek kirish signalining quwatiga bog'liq va signal kirish quwatining kamayishi bilan o'zining eng katta qiymatiga intiladi. To‘yinish quwati. Bu parametr optik kuchaytirgichning chiqish quwatining eng katta qiymatini ko'rsatadi. Tolali optik aloqa tizim- laridagi regeneratsiya punktlari oralig'idagi masofa chiqish quwatining ana shu qiymati bilan belgilanadi. Katta quwatli erbiyli tolali kuchaytirgichlarda bu ko‘rsatkich 36 dBm (4W) dan ortishi mumkin. Kuchaygan spontan nurlanish quwati. Bu parametrning mohiyatini aralashmali tolali kuchaytirgich misolida ko'rib chiqamiz. Kirish signali bo‘lmagan holda tolali optik kuchaytirgich fotonlaming spontan nurlanishi manbayi bo‘lib xizmat qiladi. Nurlanish spektirining. ko‘rinishi, biz yuqorida ko‘rib o'tganimizdek, erbiy ionlari energetik sathlarining o'zaro joylashuvi va elektronlarning bu sathlar bo'yicha statistik taqsimoti bilan belgilanadi. Spontan tarzda hosil bo'lgan fotonlar tolaning aktiv qismi bo'ylab tarqalib, o‘ziga aynan o‘xshash — o‘shanday to‘lqin uzunligi, faza qutb- lanishi va tarqalish yo‘nalishiga ega bo‘lgan fotonlar hosil qiladi. Bunday fotonlaming natijaviy spektri kuchaygan spontan nurlanish deb ataladi. Bu nurlanishning quwati 1 Hz chastotaga nisbatan boholanadi va W/Hz larda o‘lchanadi. Agar optik kuchaytirgich kirishiga lazerdan signal berilsa, spontan nurlanishning kuchayishiga olib keladigan energetik o'tishlarning bir qismi ana shu signal 177 www.ziyouz.com kutubxonasi ta’sirida yuz beradi va uning kuchayishiga olib keladi. Shunday qilib, nafaqat foydali signalning kuchayishi, shuningdek, spontan nurlanishning kuchsizlanishi ham sodir bo‘ladi (5.9-rasm). 5.9-rasm. Tolali optik kuchaytirgichning chiqish nurlanish spektri: / — kirish signal! mavjud bo ‘Imagan hoi; 2 — kirish signali mavjud bo ‘Igan hoi Kuchaytirilgan spontan nurlanishning quwati va optik kuchaytirgichning kuchaytirish koeffitsiyenti o‘rtasidagi munosabat quyidagi ifoda bilan aniqlanadi: P. , , = hvn ((7-1)/ = ri (5.6) bunda nsp — spontan emissiya koeffitsiyenti, r| - nurlanishning kvant samaradorligi (bu kattalik energetik o‘tishlar choghda har bir o'tish tufayli hosil bo‘ladigan fotonlarning o‘rtacha sonini ko'rsatadi). Download 1 Mb.
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Kamchiliklari - Optik aloqa asoslari

qo'llanish sohasining to'lqin uzunligi diapazonining 1530 — 1570 nm li oraliq bilan cheklanganligi;
kuchaytirish koeffltsiyentining to'lqin uzunligi bo'yicha notekisligi; - o'lchamlarining nisbatan kattaligi;
iste’mol quvvatining nisbatan kattaligi.
f.i.k.ning kamligi
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o'zgarishlar samaradorligining yuqori emasligi;
damlash quvvatining kattaligi (bir nechaW);
kanallar orasidagi o'tish halaqitlarining kattaligi
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f.i.k.ning kamligi;
kuchaytirish koeffltsiyentining optiktola bo'ylab tarqalayotgan yorug'likning qutblanish yo'nalishlari bo'yicha biroz o'zgarib, bir-biriga perpendikulyar yo'nalishlarda 4—8 dBga farq qilishi
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-bob. OPTIK MODULYATORLAR

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-bob. OPTIK MODULYATORLAR
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bet | 79/160 | Sana | 13.01.2024 | Hajmi | 1 Mb. | | #136728 |
Bog'liq Optik aloqa asoslari (N.Yusupov, R.Isayev)6-bob. OPTIK MODULYATORLAR
Yorug‘lik oqimini ichki va tashqi modulyatsiyalash
usullari
Ma’lumki, axborotlar oqimini optik tola bo‘ylab uzatish optik eltuvchi — yorug‘lik to‘lqinining axborot signaliga monand tarzda o‘zgartirishni taqozo etadi. Yorug'lik nurlanishning bir yoki bir necha parametrlarini elektr (tok yoki kuchlanish), tovush, mexanik yoki optik signal ta’sirida vaqt yoki fazo bo'yicha berilgan qonu- niyatga ko‘ra o‘zgartirishdan iborat mazkur jarayonni optik nurla- nishni modulyatsiyalash jarayoni deb ataladi.
Yorug‘lik nurlanishini soddalik uchun yassi monoxramatik to‘lqin deb faraz qilinsa, uning vaqt va fazo bo‘yicha tarqalishi fizik optikadan yaxshi ma’lum bo'lgan quyidagi tenglama orqali ifodalanadi:
E(x, t)=Encos[2Tt(vt—x)n/Cox+(p o)]. * (6.1)
Bu tenglamadan ko'rinadiki, optik eltuvchini axborot signaliga mos ravishda modulyatsiyalash jarayonini yorug'lik to'lqinining amplitudasi, chastotasi, fazasi va qutblanish vektorining yo‘nalishini o‘zgartirish orqali amalga oshirish mumkin. Optik signal tola bo‘ylab tarqalib, so'ngra fotoqabulqilgichga tushadi. Zamonaviy fotoqa- bulqilgichlar yorug‘lik nurlanishini faqat intensivlik bo‘yicha qayd etadi. Shu sababdan intensivlik bo‘yicha modulyatsiyalash jarayo- nidan eng keng foydalaniladi. Boshqa turdagi modulyatsiyalash jarayonlaridan foydalanilganida, dastlab u yoki bu usulda modulya- tsiyalangan nurlanishni intensivlik bo'yicha modulyatsiyalangan signalga o'zgartirish talab etiladi.
* bunda E — yorug'lik to'lqini elektr maydonining kuchlanganligi; Em — mazkur elektr maydon kuchlanganligining amplitudasi, v - tebranishlar chastotasi, t — vaqt, n — muhitning sindirish ko'rsatgichi, Co - yorug'likning vakuumdagi tezligi, x - nurlanishnig tarqalish yo'nalishi bo'yicha koordinata, (p 0 — tebranishlarning boshlang'ich fazasi.
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www.ziyouz.com kutubxonasi
Modulatsiyalangan yorug‘lik nurlanishini olishning turli xil usullari mavjud.
Ulardan birinchisi to‘g‘ridan-to‘g‘ri yoki bevosita modulyatsiya usuli bo'lib, unda yorug‘lik manbayi — yorug‘lik diodi yoki lazer diodi nurlanishining modulyatsiyasiga ulardan oqib o‘tadigan injeksiya tokini o‘zgartirish yo‘li bilan erishiladi (6.1-a rasm).
Tashqi modulyatsiya deb atalgan ikkinchi usulda yorag‘lik manbayidan tarqalayotgan o'zgarmas (modulyatsiyalanmagan) yorug‘lik oqimi maxsus qurilma — modulyator yordamida modulyatsiyalanadi (6.1-b rasm). Va nihoyat, agar tegishli modulyator bo'lsa, uni lazer rezonatoriga kiritish va shu tarzda ichki modulyatsiyani amalga oshirish mumkin (6.1-d rasm). Bundan ko‘rinadiki, ichki modulyatsiya mohiyat e’tibori bilan to‘g‘ri modulyatsiyaning bir turi hisoblanadi.
Boshqaruvchi
signal
a)
Boshqaruvchi
signal
Lazer rezonatori
Boshqaruvchi
signal
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B2B sinfidagi kodlar - Optik aloqa asoslari

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Optik aloqa asoslari
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bet | 121/160 | Sana | 13.01.2024 | Hajmi | 1 Mb. | | #136728 |
Bog'liq Optik aloqa asoslari (N.Yusupov, R.Isayev)1B2B sinfidagi kodlar. Bu sinfdagi kodlar sodda bo‘lib, boshlan- g‘ich kodlarga nisbatan liniyaga uzatiladigan impulslar soni 2 marta ortiq, shuning uchun ham samarador va keng qoMlanish topgan. RZ kodi 1B2B sinfiga kiradi. RZ kodida boshlang'ich NRZ
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www.ziyouz.com kutubxonasi
7 7.7-rasm. Raqamli TOAT energetik spektrining uzluksiz qismi
kodining «1» simvoliga T taktli intervalning birinchi yarmida mos ravishda 1 va ikkinchi yarmida 0 qo‘yiladi, ya’ni l>10 o‘zgartirish amalga oshiriladi. Boshlang‘ich NRZ kodining «0» simvoli 0>00 ga o‘zgaradi, ya’ni T taktli intervalning birinchi hamda ikkinchi yarmida liniya kodining nollari hosil bo‘ladi.
1B2B sinfdagi kodlar ichida biimpuls kodlar katta qiziqish namoyon etadi. Ular juda yuqori himoyalanganlikka va rege- . neratorlarda taktli chastotani ajralish imkoniyatiga ega.
rasmda BI-L turdagi absolut biimpuls kod ko'rsatilgan, 11.2-jadvalda (uchinchi qator) esa uning shakllanishi berilgan: boshlang‘ich «1» ikkilik ketma-ketligiga T taktli intervalning birinchi yarmida mos ravishda 1 va ikkinchi yarmida 0 qo‘yiladi, ya’ni l>10 o‘zgartirish bajariladi, «0» ikkilik ketma-ketligi uchun 0<01 turdagi o‘zgartirish bajariladi.
1B2B biimpuls kodlarining boshqa turi nisbiy biimpuls BI-S ' (11.6-rasmga qarang) kodi hisoblanadi, uning shakllanish qoidasi quyidagicha: boshlang'ich «1» ikkilik ketma-ketligiga navbatma-
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www.ziyouz.com kutubxonasi
navbat 1<11, 1 <00 turdagi o'zgarishlar mos keladi; «0» ikkilik ketma- ketligi uchun 0<10 yoki 0<01 turdagi kombinatsiyalar mos keladi.
11.2-jadval
Kod turi
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01>10>00> | 01>
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Transport protokoli toifasi 0 ( TP0 )

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Transport protokoli toifasi 0 ( TP0 )
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bet | 4/8 | Sana | 27.05.2024 | Hajmi | 0,66 Mb. | | #255230 |
Bog'liq KAMPYUTER TARMOQLARI REFTransport protokoli toifasi 0 ( TP0 ) 1-transport transport protokoli ( TP1 ) 2-transport transport protokoli ( TP2 ) 3-sinf transport protokoli ( TP3 ) 4-sinf Transport protokoli 4-sinf ( TP4 )
5-sath:Seans xizmati - ITU-T Rec. X.215 [ISO / IEC 8326] Ulanishga yo'naltirilgan seans protokoli - ITU-T Rec. X.225 [ISO / IEC 8327- 1].
Seans sathi kompyuterlar o'rtasidagi dialoglarni (ulanishlarni) boshqaradi. U lokal va uzoq dastur o'rtasidagi aloqani o'rnatadi, boshqaradi va tugatadi. U to'liq dupleks va yarim dupleksli yoki soddalashtirilgan operatsiyalarni ta'minlaydi va nazorat punktlarini o'rnatish, keyinga qoldirish, tugatish va qayta boshlash tartiblarini o'rnatadi. OSI modeli ushbu qavatni Transmit Nazorat protokolining xususiyati bo'lgan seanslarning bekamu-ko'st yopilishi, shuningdek Internet Protocol Suite-da ishlatilmaydigan seansni tekshirish va tiklash uchun javobgar qildi. Seans sathi odatda masofaviy protsedura qo'ng'iroqlaridan foydalanadigan amaliy muhitda aniq amalga oshiriladi.
6-sath:Taqdimot xizmati - ITU-T Rec. X.216 [ISO / IEC 8822] Ulanish yo'naltirilgan taqdimot protokoli - ITU-T Rec. X.226 [ISO / IEC 8823-1] Ulanishsiz taqdimot protokoli - ITU-T Rec. X.236 [ISO / IEC 9576-1]. Ushbu qatlam amaliy sathdan ma'lumotlar turlarini aniqlaydi va shifrlaydi. MIDI, MPEG va GIF kabi protokollar turli xil dasturlar tomonidan taqdim etilgan taqdimot qatlami formatlari.
7-sath: Umumiy dastur xizmatining elementlari (CASEs) Uyushma nazorati xizmati elementi (ACSE) - ITU-T Rec.X.217 [ISO / IEC 8649] , ITU-T Rec. X.227 [ISO / IEC 8650-1] , ITU-T Rec. X.237 [ISO / IEC 10035-1] . Majburiyat, kelishuv va tiklanish xizmati elementi (CCRSE) Xavfsizlik almashinuvi xizmati elementi (SESE) Bu har bir dastur boshqa dastur bilan qanday suhbatlashishini kuzatib boradi. Belgilangan manzil va manba manzillari ma'lum dasturlarga bog'langan. Majburiyat, kelishuv va tiklanish xizmati elementi (CCRSE) Xavfsizlik almashinuvi xizmati elementi (SESE) Bu har bir dastur boshqa dastur bilan qanday suhbatlashishini kuzatib boradi. Belgilangan manzil va manba manzillari ma'lum dasturlarga bog'langan.
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OSI modeli etalon model bo'lib, bu faqat nazariy jihatdan mavjud. Hozirgi kunda bu model asosida TCP/IP stek protokollariga asoslangan holda tarmoq ishlaydi

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OSI modeli etalon model bo'lib, bu faqat nazariy jihatdan mavjud. Hozirgi kunda bu model asosida TCP/IP stek protokollariga asoslangan holda tarmoq ishlaydi
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bet | 5/8 | Sana | 27.05.2024 | Hajmi | 0,66 Mb. | | #255230 |
Bog'liq KAMPYUTER TARMOQLARI REFOSI modeli etalon model bo'lib, bu faqat nazariy jihatdan mavjud. Hozirgi kunda bu model asosida TCP/IP stek protokollariga asoslangan holda tarmoq ishlaydi. TCP/IP ishlab chiqilishining yagona sababi OSI modelini soddalashtirish va qulay foydalanish hisoblanadi. TCP/IP stek protokollari tuzilishi: Bundan tashqari bizda port tushunchasi mavjud bo'lib, Port bu – mantiqiy bog'lanish tuguni hisoblanib, bu portlar yordamida mantiqiy kerakli protokolga bog'lanish hosil qilinadi. Ixtiyoriy so'rov biron manzildagi aynan kerakli portga murojaat qilinadi va javob qaytarishda esa so'rov kelgan portga qayta jo'natiladi. TCP/IP da har bir protokol uchun port mavjud. Ularning umumiy soni 65535 ta. Portlar quyidagicha bo'ladi: Bundan tashqari bizda port tushunchasi mavjud bo'lib, Port bu – mantiqiy bog'lanish tuguni hisoblanib, bu portlar yordamida mantiqiy kerakli protokolga bog'lanish hosil qilinadi. Ixtiyoriy so'rov biron manzildagi aynan kerakli portga murojaat qilinadi va javob qaytarishda esa so'rov kelgan portga qayta jo'natiladi. TCP/IP da har bir protokol uchun port mavjud. Ularning umumiy soni 65535 ta. Portlar quyidagicha bo'ladi: Fizik sath funktsiyalari tarmoqqa ulangan barcha qurilmalarda amalga oshiriladi. Kompyuter tomonidan fizik sath funktsiyalari tarmoq adapteri yoki ketma-ket port tomonidan amalga oshiriladi. Bundan tashqari, ma’lumotni tarmoqning uzatish vositasi orqali uzatish uchun qaysi uzatish texnologiyasidan foydalanilishini aniqlaydi. Protokollarning ikkinchi guruhi - bu oldindan ulanmagan (ulanishsiz) protokollar . Bunday protokollar datagram protokollari deb ham ataladi . Yuboruvchi tayyor bo`lganda xabarni oddiygina yuboradi. Xatni pochta qutisiga joylashtirish birinchi bo`lib ulanishni o`rnatmasdan aloqaning namunasidir. 3.Fizik sath funktsiyalari tarmoqqa ulangan barcha qurilmalarda amalga oshiriladi. Kompyuter tomonidan fizik sath funktsiyalari tarmoq adapteri yoki ketma-ket port tomonidan amalga oshiriladi. Bundan tashqari, ma’lumotni tarmoqning uzatish vositasi orqali uzatish uchun qaysi uzatish texnologiyasidan foydalanilishini aniqlaydi. Protokollarning ikkinchi guruhi - bu oldindan ulanmagan (ulanishsiz) protokollar . Bunday protokollar datagram protokollari deb ham ataladi . Yuboruvchi tayyor bo`lganda xabarni oddiygina yuboradi. Xatni pochta qutisiga joylashtirish birinchi bo`lib ulanishni o`rnatmasdan aloqaning namunasidir.
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Bosh sahifa
Aloqalar
Bosh sahifa
OSI modeli etalon model bo'lib, bu faqat nazariy jihatdan mavjud. Hozirgi kunda bu model asosida TCP/IP stek protokollariga asoslangan holda tarmoq ishlaydi
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Axborot xavfsizligini ta’minlash zarurati

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Axborot xavfsizligini ta’minlash zarurati
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bet | 86/118 | Sana | 17.05.2024 | Hajmi | 8,17 Mb. | | #240348 |
Bog'liq R. I. Isayev, D. X. Ibatova multimеdiali aloqa tarmoqlari toshkeAxborot xavfsizligini ta’minlash zarurati
Multiservisli aloqa tarmoqlarini yaratishda, axborot uzatishni turli vositalarini qo‘llab va turli abonent terminallari yordamida yuqori sifatli axborot almashishni ta’minlovchi funksiyalarning zarur to‘plamini kiritadi. Axborot almashishni tashkil etishda xatoliklar yuz berishi ehtimoli mavjud, ularning yuzaga kelishi butun tarmoqni va aloxida tarmoqni dasturiy-qurilmali komplekslarini ishlashining samaradorligi, shuningdek aloqa kanallaridagi (liniyalardagi) halaqitli muhit sabab bo‘ladi. Ushbu bo‘limda bunday xatoliklardan himoyalanish choralari ko‘rib chiqilmaydi. Lekin, bugungi kunda multiservisli aloqa tarmoqlarining funksional xatoliklari ostiga yashiringan, faol xujum usullari mavjud.
Butun dunyo tarixi shuni ko‘rsatadiki, turli axborotlarni izlash bo‘yicha josuslik faoliyati har qanday davlat siyosatining “asosiy asosi” hisoblanadi. Insonni bilib bo‘lmaydi, bir tomondan - atrof muhit uni, aniq shaxslar tomonidan kirish chegaralangan maxfiy axborotni izlashga jalb etishi mumkin. Boshqa tomondan – har qanday maxfiy axborotning egasi uni begonalar xavfidan saqlashni xoxlaydi. Aynan multiservisli aloqa tarmoqlarini ishlashida va foydalanishda inson omilining mavjudligi, ochiq tizimlar uchun standart vazifalar to‘plamini to‘ldirish zaruratini yuzaga keltiradi, ya’ni multiservisli aloqa tarmoqlarining xavfsizligini ta’minlash vazifasi.
Elektron kommunikatsiya insonlarni yaqinlashtiradi: vaqt va masofa yo‘qoladi. Ya’ni, xalqaro Internet Yerning millionlab aholisini birlashtiradi va juda katta axborotlar soniga ishlov beradi. Shuning uchun Internet, kompyuter josusi sohasidagi mutaxassislar uchun “faoliyat yuritishning keng maydoni” hisoblanadi.
Internet axborotni himoyalash bo‘yicha keng xizmatlar spektrini taqdim etadi. Internet foydalanuvchilari uchun shuni bilish zarurki, AQShda davlat Prezidentining “Jamiyatda shifrlashni boshqarish” (Public Encryption Management) direktivasi mavjud bo‘lib, chiqariluvchi (davlatdan tashqariga) axborotlarni himoyalashni kriptografik vositalari AQShni elektron razvedka tashkilotlari uchun axborotlarni izlashga to‘siq bo‘lmasligi kerak. Ya’ni, Internetda qo‘llaniladigan axborotni himoyalashning har qanday dasturiy va qurilmali vositalari, AQShning maxsus xizmatlari uchun “shaffof” hisoblanadi.
|
| |
Logistik servis tizimining shakllanishi

Logistik servis tizimining shakllanishi. X izm at ko ‘rsatish
sohasida korxonaning siyosatini aniqlash logistik servis tizimining
shakllanishi bilan bog‘liq va o ‘zaro b o g liq ishlar kompleksining
olib borilishini nazarda tutadi.
Logistik xizmatlar tizimini shakllantirish bo'yicha amallar quyi-
dagi ketma-ketlikda bajariladi:
l . I s t e ’m ol bozorini segm entlarga ajratish, y a ’ni uni aniq
iste’molchilar gumhiga b o lish , bu guruhlarning har biriga iste’mol
xususiyatlariga qarab m a’lum xizmatlar talab etilishi mumkin.
2. Is te ’m o lc h ila r u ch u n eng m u h im b o ‘lgan xizm atlarni
aniqlash.
3. Aniqlangan xizmatlarni saralash, iste'm olchilar uchun eng
muhim boMgan xizmatlarga e ’tiborni kuchaytirish.
4. Bozorning alohida segmentlari kelishuvida xizmatlar stan-
dartlarini aniqlash.
5. K o £rsati!ayotgan x izm atni baholash, servis darajasi va
ko'rsatilayotgan xizmatlar narxi o ‘rtasida o ‘zaro bog‘liqlikni o 'rn a-
tish, kompaniyaning raqobatbardoshligini ta ’minlash uchun zarur
bo‘lgan servis darajasini aniqlash.
6. Iste’molchilarning ehtiyojlariga xizmatlarning mos kelishini
ta’minlash uchun ular bilan aloqalarni o ‘rnatish.
Bunda iste’mol bozorining segmentlarga ajratilishi geografik
omil, ko‘rsatilayotgan xizmatlar xususiyatlari yoki boshqa ko‘rsat-
kichJar bo‘yicha amalga oshirilishi mumkin. Iste’molchilar uchun
muhim xizmatlarni aniqlash, ularni solishtirish va logistik xizmat
standartlarini aniqlash iste’molchilar o'rtasida so‘rovlar o ‘tkazish
yo‘li bilan amalga oshiriladi.
Logistik xizmat ko‘rsatishning sifat mezonlari. Logistik xizmat
ko'rsatish sifatini baholash uchun quyidagi mezonlardan foyda-
laniladi:
-
yetkazib berishning egiluvchanligi; buyurtm a bajarilish
davomiyligi,
Yetkazib berishning egiluvchanligi buyurtm a bajarilishining
kelishilgan muddati bo‘zilmagan holda, mijozni yetkazib berishning
199
birlamchi shartlarini o ‘zgartirish haqidagi xohishlaming qondirilish
darajasini xarakterlaydi. Bunga buyurtm ani o ‘tkazish shakii yoki
usulini o ‘zgartirish va boshqalar kiradi.
Yetkazib berishning ishonchliligi

Yetkazib berishning ishonchliligi yetkazib beruvchining shart-
nom ada ko‘rsatilgan buyurtm a bajarilish muddatlariga rioya qilish
imkoniyatlarini aniqlaydi. Yetkazib berishning ishonchliligiga ta ’sir
etuvchi muhim omil b o lib , shartnom ada ko‘rsati)gan majburiyat
(kafolat)laming mavjudligi hisoblanadi, bu majburiyatlarga asosan
yetkazib beruvchi buyurtm a bajarilish m uddatlari buzilgaligi uchun
javobgar b o ‘ladi.
Buyurtma bajarilish davomiyligi buyurtm a olinish vaqtidan
tovarlar partiyasini iste’molchiga yekazib borishgacha bo‘lgan Calen
dar davrini xarakterlaydi. Buyurtma bajarilish davomiyligi o ‘zining
tarkibiga quyidagilarni oladi: buyurtm ani hujjatlashtirish, ishlab
chiqarish, qadoqlash, tushirish va iste’molchiga yetkazib berish.
Sotuvdan keyingi logistik servis. Tovarlar ekspluatatsiyasining
butun m uddati davomida texnik xizmat ko‘rsatish, iste’molchilarni
o ‘qitish va axborot bilan ta ’rninlash bo ‘yicha xizmatlar kompleksini
tashkil etadi. Sotuvdan keyingi davr ichida logistik xizmat ko‘rsatish
quyidagi asosiy tadbirlam i o ‘z ichiga oladi:
• tovar sotilgandan keyin xaridorga ko'rsatiladigan xizmatlami
aniqlash;
• yetkazib berish shartlarini kelishish jarayonida sotuvdan
keyingi xizmat ko‘rsatish ketm a-ketligini o ‘rnatish;
• zarur b o ‘lgan texnik hujjatlam i tayyorlash va chiqarish tovar
iste’m olchilarm i o'qitish;
• ehtiyot qismlari ham da yetkazib berilayotgan tovarlar ustidan
nazoratni amalga oshirish imkonini beruvclii instrum entlar
va tekshiruv uskunalari bilan ta ’minlash;
• logistik xizmat ko‘rsatish jarayonini uni to ‘g‘rid an -to ‘g‘ri
amalga oshirish yo‘li bilan yoki subpudratchilar, distrebyu-
torlar (tarqatuvchilar), mijozlar tom onidan olib borilayotgan
xizm at k o ‘rsatish sifati ustidan nazorat o ‘rnatish orqali
boshqarish;
• ehtiyot qismlarini saqlash va sozlash islilarini olib borish
uchun joy va infrastrukturani aniqlash va tayyorlash;
200
• ehtiyot qismlari harakati jarayonida qadoqlash va vaqtinchalik
omborga joylashtirish,
| Chapter 7: Wireless Security Testing

them the information, which may in itself be valuable, or gets them access to a system
on the network. It’s so important to keep in mind the goal of the attacker. When we’re
testing, we need to make sure we’re not testing just for the sake of testing, though that
could be entertaining; we’re making sure that our testing targets aren’t exposed to
potential attack. The objective of your testing is to improve the security posture,
remember, and not just to knock things over.
802.11 Terminology and Functioning
Before we start in on various attacks, we should probably review the terminology and
functioning of 802.11. First, there are two types of 802.11 networks: ad hoc networks
and infrastructure networks. In an
ad hoc network
, clients connect directly to one
another. There can be multiple systems within an ad hoc network, but there is no
central device through which the communication happens. If there is an access point
(AP) or base station, the network is considered an
infrastructure network
. Devices
that connect through the AP are clients. APs will send out messages over the air indi‐
cating their presence. This message is called a
beacon
.
The process clients use to get connected to a WiFi network is to send out a message
probing for wireless networks. Whereas wired systems use electrical signals to com‐
municate, wireless systems use radio communications, meaning they have transmit‐
ters and receivers. The probe frame is sent out using the radio transmitter in the
device. Access points in the vicinity, receiving the probes, respond with their identify‐
ing information. The client, if told to by the user, will attempt to associate with the
AP. This may include some form of authentication. The authentication does not nec‐
essarily imply encryption, though WiFi networks are commonly encrypted in some
manner. This may or may not be true when it comes to public networks, such as
those in restaurants, airports, and other open spaces.
An enterprise environment may have several access points, all shar‐
ing the same service set identifier (SSID). Attacks against the wire‐
less network will be targeted at individual AP devices/radios, but
the end result, if successful, will land you on the enterprise net‐
work, regardless of which AP you are targeting.
Once the client has been authenticated and associated, it will then begin communicat‐
ing with the AP. Even if devices are communicating with others on the same wireless
network, all communication will still go through the AP rather than directly from
peer to peer. Certainly, there are far more technical details to 802.11 networks, but
this suffices for our purposes, to set the stage for later discussions.
When we do testing over the network, often the network interface needs to be put
into promiscuous mode in order to ensure that all traffic is passed up through the
network interface and to the operating system. When it comes to WiFi, we need to be
WiFi Attacks and Testing Tools | 209

concerned with another feature:
monitor mode
. This tells
the WiFi interface to send
up the radio traffic in addition to the messages that you’d normally see. This means
you could see beacon messages as well as the messages associating and authenticating
the clients to the AP. These are all the 802.11 protocol messages
that typically happen
at the radio and aren’t otherwise seen. To enable monitor mode, should the tool you
are using not do it for you, you can use
airmon_ng start wlan0
, assuming your inter‐
face name is
wlan0
. Some tools will handle the monitor mode setting for you.
Identifying Networks
One of the challenges with WiFi is that in order for systems to easily attach to the
network, the SSID is commonly broadcast. This keeps people from having to man‐
ually add the wireless network by providing the SSID, even
before having to enter the
passcode or their username and password. However, broadcasting the SSID also helps
attackers identify the wireless networks that are nearby. This is generally easy to do.
All you have to do is ask to connect to a wireless network and you’ll be presented
with a list of the available networks.
shows a list of wireless networks avail‐
able while I was at a conference in downtown Denver a few years ago. It’s a particu‐
larly
good list, so I have retained the screenshot.
War Driving
Attackers may go mobile to identify wireless networks within an
area. This process is commonly called
war driving
.
However, this list doesn’t present us with much other than the SSID. To get really use‐
ful information that we’ll
need for some of the tools, we need to look at something
like Kismet. You may be wondering what other details we need. One of them is the
base station set identifier (BSSID). This
is different from the SSID, and it looks like a
MAX address. One reason the BSSID is necessary is that an SSID can be used across
multiple access points so the SSID alone is insufficient
to indicate who a client is
communicating with.
(t) bog‘liqlik grafigi - K. J. Matkarimov b. J. Mahmudov a. A. Norqulov avtomobillarda ishlatiladigan ashyolar

|
K. J. Matkarimov b. J. Mahmudov a. A. Norqulov avtomobillarda ishlatiladigan ashyolarBog'liq K. J. Matkarimov b. J. Mahmudov a. A. Norqulov avtomobillarda is(t) bog‘liqlik grafigi.
7. 3. Suvni yumshatish usullari
Qaynatish. Suvni yumshatishning eng oddiy usuli uni 15–
20 min davomida qaynatishdir. Bunda suvga karbonat qattiqlik be-
ruvchi tuzlar qiyin eriydigan va cho‘kma hosil qiladigan karbonat
CaCO
3
va magniy gidrooksid Mg(OH)
2
larga parchalanadi, qisman
nordon karbonat gazi va kislorod ajraladi. Keyinchalik bu tuzlar fil-
trlanadi. Qoldiq vaqtinchalik qattiqlik 1–2 mg. ekv/l dan oshmaydi.
173
Suvni kimyoviy usulda yumshatish. Suvni kimyoviy usulda
yumshatishning turli usullari ancha keng tarqalgan. Bu usullardan
biri cho‘ktirish usuli bo‘lib, bunda suv tarkibidagi kalsiy va mag-
niy kationlari, eriydigan tuzlar qiyin eriydigan birikmalarga aylan-
tiriladi. Buning uchun suvga gidroksid OH
–
va karbonat CO
2–
3
ion-
lari kiritiladi. Bu maqsadda ohak Ca(OH)
2
, kalsiylangan soda Na
2
,
CO
3
va trinatriyfosfat Na
3
PO
4
ishlatiladi. Suvga solingan reagent
20–30 min davomida suv bilan aralashtiriladi. Ishlov berilganidan
so‘ng cho‘kkan quyqalar filtrlanadi, yumshagan suv esa dvigatel
ning sovitish tizimiga quyiladi. Bu usulda ishlov berishdan so‘ng
umumiy qoldiq qattiqlik 0,5–1,0 mg. ekv/l ga teng bo‘ladi.
Kation almashtirish usuli suvda erimaydigan ba’zi moddalar-
ning (kationlarning) suvni kationlar orqali filtrlashda o‘zining ka-
tionlarini tuzlar kationlariga almashtirish xususiyatiga asoslangan.
Ishlab chiqarish sharoitida suvni glaukonit yoki sun’iy permutit
birikmasi bilan yumshatish keng tarqalgan. Suv glaukonit (permu-
tit)dan filtrlab o‘tkazilganida unda o‘zgarish bo‘ladi: mineraldagi
natriy suvga o‘tadi, suvdan ajralgan kalsiy va magniy esa unda ush-
lanib qoladi. Ishlatilganida quyqa hosil qilmaydigan yumshoq suv
shu tarzda olinadi.
Glaukonit filtr 40 kg glaukonit joylashtirilgan sig‘imdan iborat
bo‘lib, undagi glaukonit qatlami 350–370 mm bo‘ladi. Filtrning
unumdorligi suvning dastlabki qattiqligi 18 mg. ekv/l bo‘lganida
250–300 l ni tashkil etadi. Ba’zan glaukonit o‘rnida permutit ishla-
tiladi va bu permutit filtr deb yuritiladi.
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Transport tarmoq yadrosida trafikni boshqarish prinsiplari

|
Transport tarmoq yadrosida trafikni boshqarish prinsiplari
|
bet | 63/118 | Sana | 17.05.2024 | Hajmi | 8,17 Mb. | | #240348 |
Bog'liq R. I. Isayev, D. X. Ibatova multimеdiali aloqa tarmoqlari toshkeTransport tarmoq yadrosida trafikni boshqarish prinsiplari
Tarmoq trafigi bir necha belgilar bo‘yicha tasniflanishi mumkin:
Internet xizmatlari va ilovalari turlari bo‘yicha (HTTP, FTP, Telnet va b.q.);
manbalar turlari bo‘yicha;
qabul qiluvchining manzili bo‘yicha;
foydalanuvchilar guruhi bo‘yicha;
Internet xizmatlari guruhi bo‘yicha;
Internet resurslari bo‘yicha (masalan, o‘ziga xos URL bo‘yicha);
yo‘nalishlar bo‘yicha (kiruvchi yoki chiquvchi);
o‘tkazish oralig‘ini boshqarish mezonlari bo‘yicha.
MPLS texnologiyasi qo‘llanilgan tarmoqlarda trafikni boshqarish imkoniyatlari.
IP/MPLS texnologiyasiga ega tarmoqlarda trafikni boshqarish quyidagi funksional vositalar va imkoniyatlarning mavjud bo‘lishini nazarda tutadi:
uzatilayotgan paketlarning birlashgan oqimlari bilan bog‘langan atributlar to‘plami;
resurslar bilan bog‘liq bo‘lgan (topologik cheklanish) atributlar to‘plami;
berilgan parametrlar to‘plamiga muvofiq marshrutni tanlashda qo‘llaniladigan cheklanishlar asosidagi marshrutlash.
Yuqorida keltirilgan barcha atributlar birgalikda boshqaruvchi o‘zgaruvchilarni ifodalaydi. Ular ma’murning harakatlari natijasida yoki avtomatik tarzda modifikatsiyalanishi mumkin.
Tarmoq faoliyati vaqtida, mazkur atributlar haqiqiy vaqt rejimida dinamik tarzda o‘zgarishi mumkin bo‘lsin.
Nazorat savollari
Telekommunikatsiyani boshqarish tarmog‘ining vazifasi nimadan iborat?
TMN arxitekturasida funksional bloklarning vazifasini tushuntiring.
TMNning fizik arxitekturasi bloklarining vazifasini tushuntiring.
LLA arxitekturasida boshqarishning nechta sathi mavjud?
Tarmoqni boshqarishni asosiy muammolari nimadan iborat?
Tarmoqni boshqarish platformasi qanday masalalarni yechish uchun moslashgan?
Tarmoqda rad etish yoki o‘ta yuklanish bo‘lgan hollarda qanday vazifalarni hal etish kerak?
Tarmoqni boshqarish jarayonida nimalar rejalashtiriladi?
Tarmoqni boshqarish masalalari nimadan iborat?
Rad etish oqibatlarini bartaraf etish qanday boshqariladi?
Taqdim etilayotgan xizmatlar sifati qanday boshqariladi?
O‘zaro hisoblashlar qanday boshqariladi?
Axborotni himoyalash qanday boshqariladi?
|
| |
Ethics Warning - Learning Kali Linux

my MAC address, I would get messages destined for you. By sending out an ARP
response indicating your IP address is at my MAC address, I put myself into the mid‐
dle of the communication flow.
This is only single-direction, though. If I end up spoofing your IP address with my
MAC address, I’m getting only messages that were supposed to go to you. To get the
other end of the conversation, I would need to spoof other addresses. You may, for
example, spoof the local gateway in order to capture messages to and from you and
the internet. This takes care of only getting the messages to me. I have to also get the
messages back out to the intended targets, or the communication just stops because
no one is getting messages they expect to get. This requires my system to forward the
initial message out to the intended target.
Since ARP caches do time out, if I don’t keep having my system sending these mes‐
sages, eventually the cache will time out and then I won’t get the messages I want any‐
more. This means that I need to keep sending out these messages, called gratuitous
ARP messages. A
gratuitous ARP message
is one that hasn’t been requested but
offered nonetheless. There are legitimate reasons for this behavior, but they aren’t
common.
While other tools can be used for this, we can use the program Ettercap. Ettercap has
two modes of functioning. The first is a curses-style interface, meaning it runs in a
console but isn’t strictly command line. It presents a character-based GUI. The other
one is a full Windows-based GUI.
Figure 2-8
shows Ettercap after our target hosts
have been selected and the ARP poisoning has been started. To start the spoofing
attack, I scanned for hosts to get all of the MAC addresses on the network. Then, I
selected the two targets and started the ARP spoofing attack.
Berkeley Packet Filters - Learning Kali Linux

A basic filter is to specify which protocol you want to capture. As an example, I could
choose to capture only TCP or UDP packets. I might also say I want to capture only
IP or other protocols. In
Example 2-12
, you can see a capture of ICMP-only packets.
You will notice that in order to apply a filter, I just put it on the end of the command
line. What results is the display of only ICMP packets. Everything still comes into the
interface and is sent up to
tcpdump
, but it then determines what to display or write
out to a file, if that’s what you are doing.
Example 2-12. tcpdump using BPF
root@rosebud:~# tcpdump icmp
tcpdump: verbose output suppressed, use -v or -vv
for
full protocol decode
listening on eth0, link-type EN10MB
(
Ethernet
)
, capture size
262144
bytes
12:01:14.602895 IP binkley.lan > rosebud.lan: ICMP
echo
request, id 8203, seq 0,
length 64
12:01:14.602952 IP rosebud.lan > binkley.lan: ICMP
echo
reply, id 8203, seq 0,
length 64
12:01:15.604118 IP binkley.lan > rosebud.lan: ICMP
echo
request, id 8203, seq 1,
length 64
12:01:15.604171 IP rosebud.lan > binkley.lan: ICMP
echo
reply, id 8203, seq 1,
length 64
12:01:16.604295 IP binkley.lan > rosebud.lan: ICMP
echo
request, id 8203, seq 2,
length 64
One thing I can do with these filters is use Boolean logic; I can use logic operators to
be able to develop complex filters. Let’s say, for instance, that I want to capture web
traffic. One way I could do that would be to say
tcp and port 80
: I am grabbing all
TCP packets that have the port as 80. You’ll notice that I don’t mention source or des‐
tination with respect to the port number. I certainly can. I could use src port 80 or dst
port 80. However, if I don’t specify source or destination, I get both ends of the con‐
versation. When a message goes out with port 80 as its destination, when the receiv‐
ing system replies, the port numbers get swapped. Port 80 on the response becomes
the source port. If I were to capture only src port 80, I wouldn’t get any of the mes‐
sages in the other direction. This may be exactly what you are looking for, of course,
but it’s something to keep in mind. You may find that you need to indicate a range of
ports to be grabbed. You could use the port-range primitive to capture a range of
ports, like 80–88, for example.
The language used for BPF provides a lot of capability. If you need really complex fil‐
ters, you can certainly look up the syntax for BPF and examples that may provide you
something specific that you are looking for. What I have often found is that specifying
the port is valuable. Also, I often know the host I want to capture traffic from. In that
case, I would use
host 192.168.86.35
to grab only traffic with that IP address. Again, I
have not specified either source or destination for the address. I could by specifying
src host or dst host. If I don’t indicate, I get both directions of the conversation.
| Chapter 2: Network Security Testing Basics

Developing even a simple understanding of BPF will help you focus what you are
looking at down to data that is relevant. When we start looking at packet captures,
you will see how complex a job it can be to do packet analysis because there are just
so many frames that contain a lot of detail to look over.
Wireshark
When you have your packet capture file, you will probably want to do some analysis.
One of the best tools for that is Wireshark. Of course, Wireshark can also capture
packets itself and generate pcap files if you want to store the capture for later analysis
or for analysis by someone else. The major advantage to Wireshark, though, is pro‐
viding a way to really dig deep into the contents of the packet. Rather than spending
time walking through what Wireshark looks like or how we can use Wireshark for
capturing packets, let’s jump into breaking apart a packet using Wireshark.
Figure 2-4
shows the IP and TCP headers from an HTTP packet.
Figure 2-4. Header fields in Wireshark
You can see from just this image that Wireshark provides far more details than we
were getting from
tcpdump
. This is one area where GUIs have a significant advantage.
There is just more room here and a better way to present the amount of data in each
of these headers. Each field in the header is presented on its own line so it’s clear what
is happening. You’ll also see here that some of the fields can be broken out even more.
The flags field, for example, can be broken open to see the details. This is because the
flags field is really a series of bits, so if you want, you can open that field by clicking
the arrow (or triangle) and you will be able to see the value of each of the bits. Of
course, you can also see what is set just by looking at the line we have presented by
Wireshark because it has done the work for us. For this frame, the Don’t Fragment bit
is set.
Another advantage to using a tool like Wireshark is that we can more easily get to the
contents of the packet. By finding a frame that we are interested in because it’s part of
a conversation that we think has some value, we just need to select Follow TCP
Stream. What we will get, in addition to only the frames that are part of that conver‐
The Scope of Wireless | 207

device to pair. This is done to support devices like earbuds
that have no ability to
accept input from the user to enter a pairing key. All of this is to say that there may be
Bluetooth devices around that attackers can connect to and pair with to extract infor‐
mation.
We perform Bluetooth testing to discover devices that are not appropriately locked
down to prevent unauthorized connections, which may result in the leakage of sensi‐
tive information. These unauthorized connections may also
provide an attacker a way
of controlling other devices, leading to a foothold inside the network.
Zigbee
Zigbee
is a protocol that has been around in concept for more than a couple of deca‐
des, though the protocol itself was ratified in 2004. Recently, Zigbee has seen a sharp
increase in implementations. This is because Zigbee was
developed as a personal area
network protocol, and the whole smart-home movement has used this simple, low-
power and low-cost protocol to allow communication throughout the house, between
devices. The point of Zigbee is to offer a way for devices that don’t
have a lot of power,
perhaps because they are battery operated, and don’t send a lot of data to communi‐
cate.
As more devices using Zigbee become available, they will increasingly become targets
of attacks. This is perhaps more
true for residential users, as more smart-home devi‐
ces are introduced to the market. It is still a concern for businesses, however, because
building automation is a thing. Zigbee is not the only protocol in this space, of
course.
Z-Wave is a related protocol, though there are no tools in Kali that will test Z-
Wave. This will likely change over time as more and more devices using Z-Wave are
introduced.
WiFi Attacks and Testing Tools
It’s hard to overstate this, so I’ll say it again: everything is wireless.
Your computer,
your tablet, your smartphone, your television, your gaming consoles,
various home
appliances, and even garage door openers are all wireless. In this context, I mean they
are wireless in the sense that they support 802.11 in one of its incarnations. Every‐
thing is connected to your network. This makes the systems themselves vulnerable,
and the prevalence of WiFi makes the underlying protocols
exposed to attack as well;
as the radio signal of your wireless network passes beyond the walls of your organiza‐
tion, attackers may be able to get access to your information. The only way they can
do that is to compromise the protocol in some way.
Ultimately, the goal of attacking WiFi networks isn’t just to attack the network; it’s to
gain access to information or systems. Or both. The attack against the protocol gets
them access to the information being transmitted across the network. This either gets
Packet Captures | 65 - Learning Kali Linux

Wireshark will also do a lot of analysis for us. As an example, when we were frag‐
menting packets earlier using
fragroute
, Wireshark would have colored frames that
weren’t right. If a packet’s checksum didn’t match, for instance, the frames belonging
to that packet would have been colored black. Any error in the protocol where the
packet is malformed would result in a frame that was colored red. Similarly, TCP
resets will get a frame colored red. A warning would be colored yellow and may result
from an application generating an unusual error code. You may also see yellow if
there are connection problems. If you want to save a little time, you can use the Ana‐
lyze menu and select Expert Info to see the entire list of frames that have been flag‐
ged. You can see a sample of this view in
Figure 2-6
.
Figure 2-6. Expert information output
Wireshark has so many capabilities; we aren’t even skimming the surface of what it
can do. A lot of what you may find it useful for is just to see the headers for each
protocol broken out in a way that you can easily read them. This will help you see
what is happening if you run into issues with your testing. One other feature I should
mention is the statistics menu. Wireshark will provide graphs and different views of
DNS Spoofing - Learning Kali Linux

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Bog'liq learningkalilinuxDNS Spoofing
One solution to the issue of needing to capture traffic that may be outside the local
network is using a DNS spoofing attack. In this attack, you interfere with a DNS
lookup to ensure that when your target attempts to resolve a hostname into an IP
address, the target gets the IP address of a system you control. This type of attack is
sometimes called a
cache poisoning attack
. The reason for this is that what you may do
is exploit a DNS server close to your target. This would generally be a caching server,
meaning it looks up addresses from authoritative servers on your behalf and then
caches the answer for a period of time determined by the authoritative server.
Once you have access to the caching server, you can modify the cache that’s in place
to direct your targets to systems that you control. You can also include any entries
that don’t exist by editing the cache. This would impact anyone who used that cach‐
ing server. This process has the benefit of working outside the local network but has
the disadvantage of requiring you to compromise a remote DNS server.
Perhaps easier, though still requiring you to be on the local network, is the program
dnsspoof
. When a system sends out a DNS request to a server, it expects a response
from that server. The request includes an identifier so it is protected against attackers
sending blind responses. If the attacker can see the request go out, though, it can cap‐
ture the identifier and include it in a response that has the IP address belonging to the
attacker.
dnsspoof
was written by Dug Song many years ago, at a time when it may
have been less likely that you would be on a switched network. If you are on a
switched network, you would have to go through the extra step of grabbing the DNS
messages in order to see the request.
Running
dnsspoof
is easy, even if preparing for running it may not be. You need a
hosts file mapping IP addresses to hostnames. This takes the form of single-line
entries with the IP address followed by spaces and then the hostname that is meant to
be associated with that IP address. Once you have the hosts file, you can run
dnsspoof
,
as you can see in
Example 2-14
.
|
| |
| Chapter 2: Network Security Testing Basics

Figure 2-8. Using Ettercap The reason for having two targets is to make sure to get both sides of a conversation.
If I poison only one party, I will get only half of the conversation. I assume that what I
want to gather is communication between my target and the internet. As a result, I set
my target as one host and the router on my network as the second host. If I needed to
acquire traffic between two systems on my network, I would select those. One would
be in Target 1, and the other would be in Target 2. In
Example 2-13
, you can see what
an ARP poison attack looks like from a packet capture. You will see the two ARP
replies where the IP addresses belong to my targets. I included a portion of the
ifcon‐ fig output on my system so you can see that the MAC address caught in the packet
capture is the MAC address of my system, where I was running the ARP spoofing
attack.
Example 2-13. tcpdump showing ARP poison attack 17:06:46.690545 ARP, Reply rosebud.lan is-at 00:0c:29:94:ce:06
(
oui Unknown
)
,
length 28
17:06:46.690741 ARP, Reply testwifi.here is-at 00:0c:29:94:ce:06
(
oui Unknown
)
,
length 28
17:06:46.786532 ARP, Request who-has localhost.lan tell savagewood.lan, length 46
^C
43
packets captured
43
packets received by filter
0
packets dropped by kernel
root@kali:~# ifconfig eth0
eth0:
flags
=
4163 mtu 1500
inet 192.168.86.227 netmask 255.255.255.0 broadcast 192.168.86.255
Poisoning Attacks | 71
inet6 fe80::20c:29ff:fe94:ce06 prefixlen
64
scopeid 0x20
ether 00:0c:29:94:ce:06 txqueuelen
1000
(
Ethernet
)
Once I have an ARP spoofing attack in place, I can capture entire conversations by
using
tcpdump or Wireshark. Keep in mind that this sort of attack works on only the
local network. This is because the MAC address is a layer 2 address so it stays on the
local network and doesn’t cross over any layer 3 boundary (moving from one network
to another). Ettercap also supports other layer 2 attacks like DHCP poisoning and
ICMP redirect attacks. Any of these may be ways to ensure you are grabbing traffic
from other systems on your local network.