{"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\/pt\/blog\/news\/dos-ataki-dlya-snizheniya-proizvoditelnosti-seti-tor","title":{"rendered":"Ataques DoS para reduzir o desempenho da rede Tor","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p>Um grupo de pesquisadores da Universidade de Georgetown e do Laborat\u00f3rio de Pesquisa da Marinha dos EUA <noindex><a rel=\"nofollow\" href=\"https:\/\/www.usenix.org\/system\/files\/sec19-jansen.pdf\">analisaram<\/a><\/noindex> a resili\u00eancia da rede an\u00f4nima Tor a ataques que levam a nega\u00e7\u00e3o de servi\u00e7o (DoS). As pesquisas sobre a comprometimento da rede Tor geralmente se concentram na censura (bloqueio de acesso ao Tor), na identifica\u00e7\u00e3o de solicita\u00e7\u00f5es atrav\u00e9s do Tor no tr\u00e1fego em tr\u00e2nsito e na an\u00e1lise da correla\u00e7\u00e3o dos fluxos de tr\u00e1fego antes do n\u00f3 de entrada e ap\u00f3s o n\u00f3 de sa\u00edda do Tor para a desanonimiza\u00e7\u00e3o dos usu\u00e1rios. O estudo apresentado mostra que a organiza\u00e7\u00e3o de ataques DoS ao Tor \u00e9 frequentemente subestimada e, com custos de alguns milhares de d\u00f3lares por m\u00eas, \u00e9 bastante vi\u00e1vel criar condi\u00e7\u00f5es que perturbem o funcionamento normal do Tor, levando os usu\u00e1rios a abandonarem o Tor devido ao desempenho insatisfat\u00f3rio.<\/p>\n<p>Os pesquisadores propuseram tr\u00eas cen\u00e1rios de ataques DoS: cria\u00e7\u00e3o de congestionamentos entre n\u00f3s de ponte, desbalanceamento de carga e cria\u00e7\u00e3o de congestionamentos entre rel\u00e9s, para os quais o atacante precisa de uma largura de banda de 30, 5 e 3 Gbit\/s, respectivamente. Em termos financeiros, o custo de realizar um ataque ao longo de um m\u00eas seria de 17, 2.8 e 1.6 mil d\u00f3lares, respectivamente. Para compara\u00e7\u00e3o, a realiza\u00e7\u00e3o de um ataque DDoS frontal para interromper o funcionamento do Tor requereria uma largura de banda de 512.73 Gbit\/s e custaria 7.2 milh\u00f5es de d\u00f3lares por m\u00eas.<\/p>\n<p>O primeiro m\u00e9todo, com um custo de 17 mil d\u00f3lares por m\u00eas, atrav\u00e9s de um ataque de inunda\u00e7\u00e3o a um conjunto limitado de n\u00f3s de ponte com uma intensidade de 30 Gbit\/s, reduzir\u00e1 a velocidade de download dos clientes em 44%. Durante os testes, apenas 12 n\u00f3s de ponte obfs4 de 38 (que n\u00e3o est\u00e3o listados em cat\u00e1logos p\u00fablicos e s\u00e3o usados para contornar o bloqueio de n\u00f3s de vigil\u00e2ncia) permaneciam operacionais, o que permite ao atacante inundar seletivamente os n\u00f3s restantes em opera\u00e7\u00e3o. Os desenvolvedores do Tor podem dobrar os custos de manuten\u00e7\u00e3o e restaurar a opera\u00e7\u00e3o dos n\u00f3s ausentes, mas para o atacante, bastaria aumentar seus gastos para 31 mil d\u00f3lares por m\u00eas para atacar todos os 38 n\u00f3s de ponte. <a class=\"wpil_keyword_link\" href=\"https:\/\/prohoster.info\/pt\/server\/\"   title=\"servidores\" data-wpil-keyword-link=\"linked\"  data-wpil-monitor-id=\"1351\">servidores<\/a> O dado o m\u00e9todo de ataque, a empresa pode ser pressionada a aumentar os custos e restaurar a opera\u00e7\u00e3o dos n\u00f3s perdidos, mas o atacante poderia simplesmente aumentar seus investimentos para 31 mil d\u00f3lares mensais para conseguir atacar todos os 38 n\u00f3s de ponte.<\/p>\n<p>O segundo m\u00e9todo, que requer 5 Gbit\/s para um ataque, baseia-se na interrup\u00e7\u00e3o do funcionamento do sistema central de medi\u00e7\u00e3o de largura de banda TorFlow e permite reduzir a m\u00e9dia de velocidade de download dos clientes em 80%. O TorFlow \u00e9 utilizado para balanceamento de carga, o que permite, durante o ataque, interromper a distribui\u00e7\u00e3o do tr\u00e1fego e for\u00e7ar seu direcionamento atrav\u00e9s de um n\u00famero limitado de servidores, causando sua sobrecarga.<\/p>\n<p>O terceiro m\u00e9todo, que exige apenas 3 Gbit\/s, baseia-se no uso de um cliente Tor modificado para criar uma carga parasit\u00e1ria, o que reduz a velocidade dos downloads dos clientes em 47% com um custo de 1,6 mil d\u00f3lares por m\u00eas. Com um aumento no or\u00e7amento do ataque para 6,3 mil d\u00f3lares, \u00e9 poss\u00edvel alcan\u00e7ar uma redu\u00e7\u00e3o de 120% na velocidade dos downloads dos clientes. O cliente modificado, em vez de construir uma cadeia padr\u00e3o de tr\u00eas n\u00f3s (n\u00f3 de entrada, n\u00f3 intermedi\u00e1rio e n\u00f3 de sa\u00edda), aplica uma cadeia de 8 n\u00f3s permitida pelo protocolo, com o n\u00famero m\u00e1ximo de saltos entre os n\u00f3s, depois solicita a download de arquivos grandes e interrompe as opera\u00e7\u00f5es de leitura ap\u00f3s enviar os pedidos, mas continua a enviar comandos de controle SENDME, instruindo os n\u00f3s de entrada a continuar a transmiss\u00e3o de dados. <\/p>\n<p>Observa-se que iniciar uma nega\u00e7\u00e3o de servi\u00e7o \u00e9 significativamente mais eficaz do que organizar um ataque DoS pelo m\u00e9todo Sybil com custos semelhantes. O m\u00e9todo Sybil implica na coloca\u00e7\u00e3o de um grande n\u00famero de rel\u00e9s pr\u00f3prios na rede Tor, onde \u00e9 poss\u00edvel descartar cadeias ou cortar a largura de banda. Com um or\u00e7amento para o ataque de 30, 5 e 3 Gbit\/s, o m\u00e9todo Sybil permite alcan\u00e7ar uma redu\u00e7\u00e3o de desempenho de 32%, 7,2% e 4,5% nos n\u00f3s de sa\u00edda, respectivamente. Enquanto isso, os ataques DoS propostos na pesquisa abrangem todos os n\u00f3s.<\/p>\n<p>Comparando os custos com outros tipos de ataques, realizar um ataque de desanonimiza\u00e7\u00e3o de usu\u00e1rios com um or\u00e7amento de 30 Gbit\/s permitir\u00e1 o controle de 21% dos n\u00f3s de entrada e 5,3% dos n\u00f3s de sa\u00edda, alcan\u00e7ando todos os n\u00f3s da cadeia em 1,1% dos casos. Para or\u00e7amentos de 5 e 3 Gbit\/s, a efic\u00e1cia ser\u00e1 de 0,06% (4,5% de n\u00f3s de entrada, 1,2% de n\u00f3s de sa\u00edda) e 0,02% (2,8% de n\u00f3s de entrada, 0,8% de n\u00f3s de sa\u00edda).<\/p>\n<p><noindex><a rel=\"nofollow\" name=\"link\"><\/a><\/noindex><\/p>\n<p>Fonte: <a \ncontent=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=51309\">opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u0413\u0440\u0443\u043f\u043f\u0430 \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 \u0414\u0436\u043e\u0440\u0434\u0436\u0442\u0430\u0443\u043d\u0441\u043a\u043e\u0433\u043e \u0443\u043d\u0438\u0432\u0435\u0440\u0441\u0438\u0442\u0435\u0442\u0430 \u0438 \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u044c\u0441\u043a\u043e\u0439 \u043b\u0430\u0431\u043e\u0440\u0430\u0442\u043e\u0440\u0438\u0438 \u0412\u041c\u0421 \u0421\u0428\u0410 \u043f\u0440\u043e\u0430\u043d\u0430\u043b\u0438\u0437\u0438\u0440\u043e\u0432\u0430\u043b\u0438 \u0441\u0442\u043e\u0439\u043a\u043e\u0441\u0442\u044c \u0430\u043d\u043e\u043d\u0438\u043c\u043d\u043e\u0439 \u0441\u0435\u0442\u0438 Tor \u043a \u0430\u0442\u0430\u043a\u0430\u043c, \u043f\u0440\u0438\u0432\u043e\u0434\u044f\u0449\u0438\u043c \u043a \u043e\u0442\u043a\u0430\u0437\u0443 \u0432 \u043e\u0431\u0441\u043b\u0443\u0436\u0438\u0432\u0430\u043d\u0438\u0438 (DoS). \u0418\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u043d\u0438\u044f \u0432 \u043e\u0431\u043b\u0430\u0441\u0442\u0438 \u043a\u043e\u043c\u043f\u0440\u043e\u043c\u0435\u0442\u0430\u0446\u0438\u0438 \u0441\u0435\u0442\u0438 Tor \u0432 \u043e\u0441\u043d\u043e\u0432\u043d\u043e\u043c \u0441\u0442\u0440\u043e\u044f\u0442\u0441\u044f \u0432\u043e\u043a\u0440\u0443\u0433 \u0446\u0435\u043d\u0437\u0443\u0440\u0438\u0440\u043e\u0432\u0430\u043d\u0438\u044f (\u0431\u043b\u043e\u043a\u0438\u0440\u043e\u0432\u0430\u043d\u0438\u044f \u0434\u043e\u0441\u0442\u0443\u043f\u0430 \u043a Tor), \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0435\u043d\u0438\u044f \u0437\u0430\u043f\u0440\u043e\u0441\u043e\u0432 \u0447\u0435\u0440\u0435\u0437 Tor \u0432 \u0442\u0440\u0430\u043d\u0437\u0438\u0442\u043d\u043e\u043c \u0442\u0440\u0430\u0444\u0438\u043a\u0435 \u0438 \u0430\u043d\u0430\u043b\u0438\u0437\u0430 \u043a\u043e\u0440\u0440\u0435\u043b\u044f\u0446\u0438\u0438 \u043f\u043e\u0442\u043e\u043a\u043e\u0432 \u0442\u0440\u0430\u0444\u0438\u043a\u0430 \u043f\u0435\u0440\u0435\u0434 \u0432\u0445\u043e\u0434\u043d\u044b\u043c \u0443\u0437\u043b\u043e\u043c \u0438 \u043f\u043e\u0441\u043b\u0435 \u0432\u044b\u0445\u043e\u0434\u043d\u043e\u0433\u043e [&hellip;]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-37276","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.3 - aioseo.com -->\n\t<meta name=\"description\" content=\"\u0413\u0440\u0443\u043f\u043f\u0430 \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 \u0414\u0436\u043e\u0440\u0434\u0436\u0442\u0430\u0443\u043d\u0441\u043a\u043e\u0433\u043e \u0443\u043d\u0438\u0432\u0435\u0440\u0441\u0438\u0442\u0435\u0442\u0430 \u0438 \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u044c\u0441\u043a\u043e\u0439 \u043b\u0430\u0431\u043e\u0440\u0430\u0442\u043e\u0440\u0438\u0438 \u0412\u041c\u0421 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