DNS Fieldsedit

Fields describing DNS queries and answers.

DNS events should either represent a single DNS query prior to getting answers (dns.type:query) or they should represent a full exchange and contain the query details as well as all of the answers that were provided for this query (dns.type:answer).

DNS Field Detailsedit

FieldDescriptionLevel

dns.answers

An array containing an object for each answer section returned by the server.

The main keys that should be present in these objects are defined by ECS. Records that have more information may contain more keys than what ECS defines.

Not all DNS data sources give all details about DNS answers. At minimum, answer objects must contain the data key. If more information is available, map as much of it to ECS as possible, and add any additional fields to the answer objects as custom fields.

type: object

extended

dns.answers.class

The class of DNS data contained in this resource record.

type: keyword

example: IN

extended

dns.answers.data

The data describing the resource.

The meaning of this data depends on the type and class of the resource record.

type: keyword

example: 10.10.10.10

extended

dns.answers.name

The domain name to which this resource record pertains.

If a chain of CNAME is being resolved, each answer’s name should be the one that corresponds with the answer’s data. It should not simply be the original question.name repeated.

type: keyword

example: www.google.com

extended

dns.answers.ttl

The time interval in seconds that this resource record may be cached before it should be discarded. Zero values mean that the data should not be cached.

type: long

example: 180

extended

dns.answers.type

The type of data contained in this resource record.

type: keyword

example: CNAME

extended

dns.header_flags

Array of 2 letter DNS header flags.

Expected values are: AA, TC, RD, RA, AD, CD, DO.

type: keyword

example: ['RD', 'RA']

extended

dns.id

The DNS packet identifier assigned by the program that generated the query. The identifier is copied to the response.

type: keyword

example: 62111

extended

dns.op_code

The DNS operation code that specifies the kind of query in the message. This value is set by the originator of a query and copied into the response.

type: keyword

example: QUERY

extended

dns.question.class

The class of of records being queried.

type: keyword

example: IN

extended

dns.question.name

The name being queried.

If the name field contains non-printable characters (below 32 or above 126), those characters should be represented as escaped base 10 integers (\DDD). Back slashes and quotes should be escaped. Tabs, carriage returns, and line feeds should be converted to \t, \r, and \n respectively.

type: keyword

example: www.google.com

extended

dns.question.registered_domain

The highest registered domain, stripped of the subdomain.

For example, the registered domain for "foo.google.com" is "google.com".

This value can be determined precisely with a list like the public suffix list (http://publicsuffix.org). Trying to approximate this by simply taking the last two labels will not work well for TLDs such as "co.uk".

type: keyword

example: google.com

extended

dns.question.subdomain

The subdomain is all of the labels under the registered_domain.

If the domain has multiple levels of subdomain, such as "sub2.sub1.example.com", the subdomain field should contain "sub2.sub1", with no trailing period.

type: keyword

example: www

extended

dns.question.top_level_domain

The effective top level domain (eTLD), also known as the domain suffix, is the last part of the domain name. For example, the top level domain for google.com is "com".

This value can be determined precisely with a list like the public suffix list (http://publicsuffix.org). Trying to approximate this by simply taking the last label will not work well for effective TLDs such as "co.uk".

type: keyword

example: co.uk

extended

dns.question.type

The type of record being queried.

type: keyword

example: AAAA

extended

dns.resolved_ip

Array containing all IPs seen in answers.data.

The answers array can be difficult to use, because of the variety of data formats it can contain. Extracting all IP addresses seen in there to dns.resolved_ip makes it possible to index them as IP addresses, and makes them easier to visualize and query for.

type: ip

example: ['10.10.10.10', '10.10.10.11']

extended

dns.response_code

The DNS response code.

type: keyword

example: NOERROR

extended

dns.type

The type of DNS event captured, query or answer.

If your source of DNS events only gives you DNS queries, you should only create dns events of type dns.type:query.

If your source of DNS events gives you answers as well, you should create one event per query (optionally as soon as the query is seen). And a second event containing all query details as well as an array of answers.

type: keyword

example: answer

extended