zeek/policy/protocols/dns/detect.bro
Seth Hall 04aa03e4ab New default notice actions for emailing network admins.
- When ACTION_EMAIL_ADMIN_ORIG or ACTION_EMAIL_ADMIN_RESP
  is applied to a notice,
  the email addresses associated with the address
  are collected from the new local_admins table
  and the email is sent to all discovered email addresses.
- The site.bro script is now in the Site module.
- Some other small cleanup.
2011-06-25 01:17:09 -04:00

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##! Script for detecting strange activity within DNS.
##!
##! Notices raised:
##!
##! * :bro:enum:`DNS::DNS_ExternalName`
##!
##! A remote host resolves to a local host, but the name is not considered
##! to be within a local zone. :bro:id:`local_zones` variable **must**
##! be set appropriately for this detection.
@load dns/base
@load notice
module DNS;
export {
redef enum Notice::Type += {
## Raised when a non-local name is found to be pointing at a local host.
## This only works appropriately when all of your authoritative DNS
## servers are located in your :bro:id:`Site::local_nets`.
DNS_ExternalName,
};
}
event dns_A_reply(c: connection, msg: dns_msg, ans: dns_answer, a: addr) &priority=-3
{
if ( |Site::local_zones| == 0 )
return;
# Check for responses from remote hosts that point at local hosts
# but the name is not considered to be within a "local" zone.
if ( Site::is_local_addr(a) && # referring to a local host
!Site::is_local_addr(c$id$resp_h) && # response from an external nameserver
!Site::is_local_name(ans$query) ) # name isn't in a local zone.
{
NOTICE([$note=DNS_ExternalName,
$msg=fmt("%s is pointing to a local host - %s.", ans$query, a),
$conn=c]);
}
}