-- Catch DNS traffic going to machines other than the host-configured DNS server (event-based) -- -- references: -- * https://attack.mitre.org/techniques/T1071/004/ (C2: Application Layer Protocol: DNS) -- -- interval: 120 -- tags: persistent events net -- -- NOTE: The interval above must match WHERE clause to avoid missing events -- -- This only supports IPv4 traffic due to an osquery bug with 'dns_resolvers' -- The non-event version is unexpected-dns-traffic.sql SELECT protocol, s.remote_port, s.remote_address, s.action, s.status, p.name, p.path, p.cmdline AS child_cmd, p.cwd, s.pid, p.parent AS parent_pid, pp.cmdline AS parent_cmd, hash.sha256, CONCAT (p.name, ',', remote_address, ',', remote_port) AS exception_key FROM socket_events s LEFT JOIN processes p ON s.pid = p.pid LEFT JOIN processes pp ON p.parent = pp.pid LEFT JOIN hash ON p.path = hash.path WHERE s.time > (strftime('%s', 'now') -120) AND remote_port IN (53, 5353) AND remote_address NOT LIKE '%:%' AND s.remote_address NOT LIKE '172.1%' AND s.remote_address NOT LIKE '172.2%' AND s.remote_address NOT LIKE '172.30.%' AND s.remote_address NOT LIKE '172.31.%' AND s.remote_address NOT LIKE '10.%' AND s.remote_address NOT LIKE '192.168.%' AND s.remote_address NOT LIKE '127.%' AND remote_address NOT IN ( SELECT DISTINCT address FROM dns_resolvers WHERE type = 'nameserver' and address != '' ) -- systemd-resolve sometimes shows up this way -- If we could narrow this down using 'sys_resolvers' I would, but it is misuse of GROUP_CONCAT AND NOT ( s.pid = -1 AND s.remote_port = 53 and p.parent = '' ) -- Some applications hard-code a safe DNS resolver, or allow the user to configure one AND s.remote_address NOT IN ( '100.100.100.100', -- Tailscale Magic DNS '1.1.1.1', -- Cloudflare '1.1.1.2', -- Cloudflare '8.8.8.8', -- Google '8.8.4.4', -- Google (backup) '4.2.2.1', -- Level 3 '4.2.2.2', -- Level 3 '4.2.2.3', -- Level 3 '4.2.2.4', -- Level 3 '4.2.2.5', -- Level 3 '4.2.2.6', -- Level 3 '208.67.220.220', -- OpenDNS '208.67.222.222', -- OpenDNS '208.67.222.123', -- OpenDNS '75.75.75.75', -- Comcast '75.75.76.76', -- Comcast '68.105.28.13', -- Cox '80.248.7.1' -- 21st Century (NG) ) -- Exceptions that specifically talk to one server AND exception_key NOT IN ( 'coredns,0.0.0.0,53', 'syncthing,46.162.192.181,53', 'Code Helper,208.67.222.123,53', 'chrome,74.125.250.47,53', 'Jabra Direct Helper,208.67.222.123,53' ) AND p.name != 'nessusd' -- Local DNS servers and custom clients go here AND p.path NOT IN ( '/usr/lib/systemd/systemd-resolved', '/Library/Nessus/run/sbin/nessusd', '/usr/bin/apko', '/opt/google/chrome/chrome', '/Applications/Slack.app/Contents/Frameworks/Slack Helper.app/Contents/MacOS/Slack Helper', '/Applications/Spotify.app/Contents/Frameworks/Spotify Helper.app/Contents/MacOS/Spotify Helper' ) -- Chromium apps can send stray DNS packets AND p.path NOT LIKE '/Applications/Google Chrome.app/Contents/Frameworks/Google Chrome Framework.framework/Versions/%/Helpers/Google Chrome Helper.app/Contents/MacOS/Google Chrome Helper' AND p.path NOT LIKE '/Applications/Brave Browser.app/Contents/Frameworks/Brave Browser Framework.framework/Versions/%/Helpers/Brave Browser Helper.app/Contents/MacOS/Brave Browser Helper' -- Workaround for the GROUP_CONCAT subselect adding a blank ent GROUP BY s.remote_address, s.remote_port HAVING remote_address != ''