{"id":629,"date":"2012-01-06T13:15:21","date_gmt":"2012-01-06T13:15:21","guid":{"rendered":"https:\/\/fir3netwp.gmsrrpobkbd.com\/2012\/01\/06\/mpf-framework\/"},"modified":"2021-07-24T18:21:18","modified_gmt":"2021-07-24T18:21:18","slug":"mpf-framework","status":"publish","type":"post","link":"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html","title":{"rendered":"Mitigating DoS attacks on a Cisco ASA"},"content":{"rendered":"<p>Within this example we will configure modular policy framework to define a range of connection limits. This provides a basic means of protecting your environment against DoS attacks.<\/p>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_65 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<p class=\"ez-toc-title\">Table of Contents<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-662d2abaf030f\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-662d2abaf030f\"  aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html\/#Define_Traffic\" title=\"Define Traffic\">Define Traffic<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html\/#Create_Class-map\" title=\"Create Class-map\">Create Class-map<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html\/#Create_Policy-map\" title=\"Create Policy-map\">Create Policy-map<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html\/#Assign_to_Interface\" title=\"Assign to Interface\">Assign to Interface<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html\/#Note_around_TCP_Intercept\" title=\"Note around TCP Intercept\">Note around TCP Intercept<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html\/#Note_around_connection_limits\" title=\"Note around connection limits\">Note around connection limits<\/a><\/li><\/ul><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2 class=\"h3\"><span class=\"ez-toc-section\" id=\"Define_Traffic\"><\/span><strong>Define Traffic<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>First of all we define which traffic the MPF policy will be applied to. In the example below we exclude the host 8.8.8.8 whilst inspecting all other traffic.<\/p>\n<p class=\"codemulti\">cisco-asa(config)# access-list mpf-policy-acl extended deny ip host 8.8.8.8 any<br \/>cisco-asa(config)# access-list mpf-policy-acl extended permit ip any any<\/p>\n<h2 class=\"h3\"><span class=\"ez-toc-section\" id=\"Create_Class-map\"><\/span><strong>Create Class-map<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Next we assign the previously created access-list to a class-map.<\/p>\n<p class=\"codemulti\">cisco-asa(config)# class-map mpf-policy<br \/>cisco-asa(config-cmap)# match access-list mpf-policy-acl<br \/>cisco-asa(config-cmap)# exit<\/p>\n<h2 class=\"h3\"><span class=\"ez-toc-section\" id=\"Create_Policy-map\"><\/span><strong>Create Policy-map<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Then a policy-map is created and the necessary connection limits defined.<\/p>\n<p class=\"codemulti\">cisco-asa(config)# policy-map mpf-policy-map<br \/>cisco-asa(config-pmap)# class mpf-policy<br \/>cisco-asa(config-pmap-c)# set connection conn-max 9500<br \/>cisco-asa(config-pmap-c)# set connection embryonic-conn-max 5000<br \/>cisco-asa(config-pmap-c)# set connection per-client-embryonic-max 100<br \/>cisco-asa(config-pmap-c)# set connection per-client-max 75<br \/>cisco-asa(config-pmap-c)# exit<br \/>cisco-asa(config-pmap)# exit<\/p>\n<h2 class=\"h3\"><span class=\"ez-toc-section\" id=\"Assign_to_Interface\"><\/span><strong>Assign to Interface<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Finally the policy map is assigned against a service-policy and interface<\/p>\n<p class=\"codemulti\">cisco-asa(config)# service-policy mpf-policy-map interface outside<\/p>\n<p>&nbsp;<\/p>\n<h4><span class=\"ez-toc-section\" id=\"Note_around_TCP_Intercept\"><\/span><strong>Note around TCP Intercept<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n<p><strong><em><\/em><\/strong>When configuring embryonic connections either via MPF (or within the NAT statement) at the point the threshold is reached TCP Intercept is enabled. This feature then :<\/p>\n<ol>\n<li>intercepts the initial SYN from going to the backend server, and only forwards the connection once the 3-way handshake is complete,<\/li>\n<li>builds a SYN cookie based on head information within the packet, and a password (only known to the ASA). Which is uses as a sequence number within the SYN-ACK. This method means no&nbsp;resources (i.e the connection table) are used to store the half open connection.<\/li>\n<\/ol>\n<h4><span class=\"ez-toc-section\" id=\"Note_around_connection_limits\"><\/span><strong>Note around connection limits<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n<p>Its also good to know when applying connection limits within a policy map that it only applies to fully established connections. Meaning should one side half close the connection (i.e with a FIN), such as the attacker, then these (half closed) connections would not count within the current connection count within MPF. In turn allowing further connections could be sent through the firewall.<\/p>\n<p>This only really presents an issue with poorly built applications, where the server side does not close its side of the connection and in most cases this caveat doesn&#8217;t present an issue.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Within this example we will configure modular policy framework to define a range of connection limits. This provides a basic means of protecting your environment against DoS attacks. Define Traffic First of all we define which traffic the MPF policy will be applied to. In the example below we exclude the host 8.8.8.8 whilst inspecting &#8230; <a title=\"Mitigating DoS attacks on a Cisco ASA\" class=\"read-more\" href=\"https:\/\/www.fir3net.com\/Firewalls\/Cisco\/mpf-framework.html\" aria-label=\"Read more about Mitigating DoS attacks on a Cisco ASA\">Read more<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Mitigating DoS attacks on a Cisco ASA - Fir3net<\/title>\n<meta name=\"description\" content=\"Within this example we will configure modular policy framework to define a range of connection limits. 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