DNS Query To Recently Created Domain

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 * Copyright 2023 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

rule dns_query_to_recently_created_domain {

  meta:
    author = "Google Cloud Security"
    description = "DNS query to a recently created domain"
    rule_id = "mr_a5cff3f1-8092-48a0-b4a3-f3f856299474"
    rule_name = "DNS Query To Recently Created Domain"
    type = "alert"
    tags = "whois"
    data_source = "microsoft sysmon"
    severity = "Low"
    priority = "Low"

  events:
    $dns.metadata.event_type = "NETWORK_DNS"
    $dns.network.dns.questions.name = $dns_query
    $dns.principal.user.userid = $user

    // whois data provided by GCTI
    $whois.graph.entity.hostname = $dns_query
    $whois.graph.metadata.entity_type = "DOMAIN_NAME"
    $whois.graph.metadata.vendor_name = "WHOIS"
    $whois.graph.entity.domain.creation_time.seconds > 0
    // domain was created in the last 30 days
    2592000 > timestamp.current_seconds() - $whois.graph.entity.domain.creation_time.seconds

  match:
    $user over 1h

  outcome:
   $risk_score = max(35)
   $event_count = count_distinct($dns.metadata.id)
   $network_dns_questions_name = array_distinct($dns.network.dns.questions.name)
   $network_dns_answers_data = array_distinct($dns.network.dns.answers.data)
   // added to populate alert graph with additional context
   $principal_ip = array_distinct($dns.principal.ip)
   $target_ip = array_distinct($dns.target.ip)
   $principal_process_pid = array_distinct($dns.principal.process.pid)
   $principal_process_file_full_path = array_distinct($dns.principal.process.file.full_path)
   $principal_process_product_specific_process_id = array_distinct($dns.principal.process.product_specific_process_id)
   $principal_process_command_line = array_distinct($dns.principal.process.command_line)
   $principal_process_file_sha256 = array_distinct($dns.principal.process.file.sha256)
   $principal_process_parent_process_product_specific_process_id = array_distinct($dns.principal.process.parent_process.product_specific_process_id)
   // Commented out principal.user.userid because it is already represented in graph as match variable. If match changes, can uncomment to add to results
   //$principal_user_userid = array_distinct($dns.principal.user.userid)

  condition:
    $dns and $whois
}