{"id":37276,"date":"2019-10-31T22:16:42","date_gmt":"2019-10-31T19:16:42","guid":{"rendered":"https:\/\/prohoster.info\/blog\/dos-ataki-dlya-snizheniya-proizvoditelnosti-seti-tor\/"},"modified":"2019-10-31T22:16:42","modified_gmt":"2019-10-31T19:16:42","slug":"dos-ataki-dlya-snizheniya-proizvoditelnosti-seti-tor","status":"publish","type":"post","link":"https:\/\/prohoster.info\/ro\/blog\/news\/dos-ataki-dlya-snizheniya-proizvoditelnosti-seti-tor","title":{"rendered":"Atacuri DoS pentru reducerea performan\u021bei re\u021belei Tor","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

O grup de cercet\u0103tori de la Universitatea Georgetown \u0219i de la laboratorul de cercetare al Marinei Americane au analizat<\/a><\/noindex> rezisten\u021ba re\u021belei anonime Tor la atacurile de tip denial of service (DoS). Cercet\u0103rile privind compromiterea re\u021belei Tor se concentreaz\u0103 \u00een principal pe cenzurarea (blocarea accesului la Tor), pe identificarea cererilor prin Tor \u00een traficul de tranzit \u0219i pe analiza corela\u021biei fluxurilor de trafic \u00eenainte de nodul de intrare \u0219i dup\u0103 nodul de ie\u0219ire Tor pentru de-anonimizarea utilizatorilor. Studiul prezentat arat\u0103 c\u0103 organizarea atacurilor DoS \u00eempotriva Tor este neglijat\u0103 \u0219i c\u0103, cu un cost de c\u00e2teva mii de dolari pe lun\u0103, este realizabil s\u0103 se creeze condi\u021bii care s\u0103 afecteze func\u021bionarea normal\u0103 a Tor, oblig\u00e2nd utilizatorii s\u0103 \u00eenceteze utilizarea Tor din cauza performan\u021bei slabe.<\/p>\n

Cercet\u0103torii au propus trei scenarii de desf\u0103\u0219urare a atacurilor DoS: crearea de congestii \u00eentre nodurile bridge, dezechilibrarea sarcinii \u0219i generarea de congestii \u00eentre relee, pentru care atacatorul trebuie s\u0103 dispun\u0103 de o l\u0103\u021bime de band\u0103 de 30, 5 \u0219i respectiv 3 Gbit\/s. \u00cen termeni financiari, costul desf\u0103\u0219ur\u0103rii unui atac pe parcursul unei luni va fi de 17, 2.8 \u0219i 1.6 mii de dolari, respectiv. Spre compara\u021bie, desf\u0103\u0219urarea unui atac DDoS direct pentru a afecta func\u021bionarea Tor ar necesita o l\u0103\u021bime de band\u0103 de 512.73 Gbit\/s \u0219i ar costa 7.2 milioane de dolari pe lun\u0103.<\/p>\n

Prima metod\u0103, cu un cost de 17 mii de dolari pe lun\u0103, prin inundarea unui set limitat de noduri bridge cu o intensitate de 30 Gbit\/s, va reduce viteza de desc\u0103rcare a datelor de c\u0103tre clien\u021bi cu 44%. \u00cen cadrul testelor, au r\u0103mas func\u021bionale doar 12 noduri bridge obfs4 din 38 (neincluse \u00een listele publice \u0219i utilizate pentru a ocoli blocarea nodurilor de verificare), ceea ce permite eliminarea selec\u021bionat\u0103 a nodurilor bridge r\u0103mase prin inunda\u021bie. Dezvoltatorii Tor pot dubla costurile de \u00eentre\u021binere \u0219i pot restabili func\u021bionarea nodurilor lips\u0103, dar atacatorului \u00eei va fi suficient s\u0103 \u00ee\u0219i creasc\u0103 cheltuielile la 31 de mii de dolari pe lun\u0103 pentru a desf\u0103\u0219ura un atac asupra tuturor celor 38 de noduri bridge. servere<\/a> Cordial<\/p>\n

A doua metod\u0103, care necesit\u0103 5 Gbit\/s pentru atac, se bazeaz\u0103 pe compromiterea sistemului centralizat de m\u0103surare a l\u0103\u021bimii de band\u0103 TorFlow \u0219i permite reducerea vitezei medii de desc\u0103rcare a datelor de c\u0103tre clien\u021bi cu 80%. TorFlow este utilizat pentru echilibrarea sarcinii, ceea ce permite, \u00een cadrul atacului, compromiterea distribu\u021biei traficului \u0219i organizarea acestuia printr-un num\u0103r limitat de servere, cauz\u00e2ndu-le supra\u00eenc\u0103rcare.<\/p>\n

A treia metod\u0103, care necesit\u0103 doar 3 Gbit\/s, se bazeaz\u0103 pe utilizarea unui client Tor modificat pentru a crea o \u00eenc\u0103rc\u0103tur\u0103 parazitar\u0103, ceea ce permite reducerea vitezei desc\u0103rc\u0103rilor clien\u021bilor cu 47% la un cost de 1.6 mii dolari pe lun\u0103. Prin cre\u0219terea cheltuielilor pentru atac la 6.3 mii dolari, se poate ob\u021bine o reducere a vitezei desc\u0103rc\u0103rilor clien\u021bilor cu 120%. Clientul modificat, \u00een loc s\u0103 construiasc\u0103 o lan\u021b de trei noduri (noddul de intrare, nodul intermediar \u0219i nodul de ie\u0219ire), utilizeaz\u0103 un lan\u021b de 8 noduri permis de protocol, cu un num\u0103r maxim de hop-uri \u00eentre noduri, dup\u0103 care solicit\u0103 desc\u0103rcarea fi\u0219ierelor mari \u0219i suspend\u0103 opera\u021biunile de citire dup\u0103 trimiterea cererilor, dar continu\u0103 s\u0103 trimit\u0103 comenzi de control SENDME, instruct\u00e2nd nodurile de intrare s\u0103 continue transmiterea datelor. <\/p>\n

Se remarc\u0103 faptul c\u0103 ini\u021bierea unui atac de refuz al serviciului este semnificativ mai eficient\u0103 dec\u00e2t organizarea unui atac DoS prin metoda Sybil, av\u00e2nd costuri similare. Metoda Sybil implic\u0103 plasarea \u00een re\u021beaua Tor a unui num\u0103r mare de propriile relee, pe care se pot respinge lan\u021burile sau se poate limita l\u0103\u021bimea de band\u0103. Av\u00e2nd un buget pentru atac de 30, 5 \u0219i 3 Gbit\/s, metoda Sybil permite ob\u021binerea unei reduceri a performan\u021bei pentru 32%, 7.2% \u0219i 4.5% din nodurile de ie\u0219ire, respectiv. \u00cen timp ce atacurile DoS propuse \u00een cadrul studiului acoper\u0103 toate nodurile.<\/p>\n

Compar\u00e2nd costurile cu alte tipuri de atacuri, desf\u0103\u0219urarea unui atac de deanonimizare a utilizatorilor cu un buget de 30 Gbit\/s va permite controlul asupra 21% nodurilor de intrare \u0219i 5.3% nodurilor de ie\u0219ire, av\u00e2nd o acoperire a tuturor nodurilor din lan\u021b \u00een 1.1% din cazuri. Pentru bugetele de 5 \u0219i 3 Gbit\/s, eficien\u021ba va fi de 0.06% (4.5% din nodurile de intrare, 1.2% din nodurile de ie\u0219ire) \u0219i 0.02% (2.8% din nodurile de intrare, 0.8% din nodurile de ie\u0219ire).<\/p>\n

<\/a><\/noindex><\/p>\n

Sursa: opennet.ro<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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