{"description": "To make Avahi ignore packets unless the TTL field is 255, edit\n<tt>/etc/avahi/avahi-daemon.conf</tt> and ensure the following line\nappears in the <tt>[server]</tt> section:\n<pre>check-response-ttl=yes</pre>", "rationale": "This helps to ensure that only mDNS responses from the local network are\nprocessed, because the TTL field in a packet is decremented from its initial\nvalue of 255 whenever it is routed from one network to another. Although a\nproperly-configured router or firewall should not allow mDNS packets into\nthe local network at all, this option provides another check to ensure they\nare not permitted.", "severity": "low", "references": {"cis-csc": ["11", "14", "3", "9"], "cobit5": ["BAI10.01", "BAI10.02", "BAI10.03", "BAI10.05", "DSS05.02", "DSS05.05", "DSS06.06"], "isa-62443-2009": ["4.3.3.5.1", "4.3.3.5.2", "4.3.3.5.3", "4.3.3.5.4", "4.3.3.5.5", "4.3.3.5.6", "4.3.3.5.7", "4.3.3.5.8", "4.3.3.6.1", "4.3.3.6.2", "4.3.3.6.3", "4.3.3.6.4", "4.3.3.6.5", "4.3.3.6.6", "4.3.3.6.7", "4.3.3.6.8", "4.3.3.6.9", "4.3.3.7.1", "4.3.3.7.2", "4.3.3.7.3", "4.3.3.7.4", "4.3.4.3.2", "4.3.4.3.3"], "isa-62443-2013": ["SR 1.1", "SR 1.10", "SR 1.11", "SR 1.12", "SR 1.13", "SR 1.2", "SR 1.3", "SR 1.4", "SR 1.5", "SR 1.6", "SR 1.7", "SR 1.8", "SR 1.9", "SR 2.1", "SR 2.2", "SR 2.3", "SR 2.4", "SR 2.5", "SR 2.6", "SR 2.7", "SR 7.6"], "iso27001-2013": ["A.12.1.2", "A.12.5.1", "A.12.6.2", "A.14.2.2", "A.14.2.3", "A.14.2.4", "A.9.1.2"], "nist": ["CM-6(a)"], "nist-csf": ["PR.IP-1", "PR.PT-3"]}, "control_references": {}, "components": [], "identifiers": {}, "ocil_clause": null, "ocil": null, "oval_external_content": null, "fixtext": "", "checktext": "", "vuldiscussion": "", "srg_requirement": "", "warnings": [], "conflicts": [], "requires": [], "policy_specific_content": {}, "platform": null, "platforms": [], "sce_metadata": {}, "inherited_platforms": [], "cpe_platform_names": [], "inherited_cpe_platform_names": [], "bash_conditional": null, "fixes": {}, "title": "Check Avahi Responses' TTL Field", "definition_location": "/aptdata/openscap/scap-security-guide/linux_os/guide/services/avahi/avahi_configuration/avahi_check_ttl/rule.yml", "template": null}