WHOIS Expired Domain Accessed

// Copyright 2023 Google LLC. Licensed under Apache-2.0.

rule whois_expired_domain_accessed {

  meta:
    author = "Google Cloud Security"
    description = "Example usage of WHOIS data, detecting an executable file download from a domain that's recently expired"
    rule_id = "mr_7b487c4f-cbf9-4b11-8b25-632ada3f90a3"
    rule_name = "WHOIS Expired Domain Accessed"
    type = "alert"
    tags = "whois"
    data_source = "zscalar"
    severity = "Low"
    priority = "Low"

  events:
    $access.metadata.event_type = "NETWORK_HTTP"
    $access.target.hostname = $hostname

    // join access event to entity graph to use WHOIS data
    $whois.graph.entity.domain.name = $hostname

    // Whois domains provided by GCTI Feed
    $whois.graph.metadata.entity_type = "DOMAIN_NAME"
    $whois.graph.metadata.vendor_name = "WHOIS"
    $whois.graph.metadata.product_name = "WHOISXMLAPI Simple Whois"
    $whois.graph.metadata.source_type = "GLOBAL_CONTEXT"
    // Filter out domains without expiration time
    $whois.graph.entity.domain.expiration_time.seconds > 0
    // Domain expired before the event
    $whois.graph.entity.domain.expiration_time.seconds < $access.metadata.event_timestamp.seconds

  match:
    $hostname over 1h

  outcome:
    $risk_score = 20
    $event_count = count_distinct($access.metadata.id)
    //added to populate alert graph with additional context
    $principal_hostname = array_distinct($access.principal.hostname)
    // Commented out principal.hostname because it is already represented in graph as match variable. If match changes, can uncomment to add to results
    //$target_hostname = array_distinct($access.target.hostname)
    $principal_process_pid = array_distinct($access.principal.process.pid)
    $principal_process_command_line = array_distinct($access.principal.process.command_line)
    $principal_process_file_sha256 = array_distinct($access.principal.process.file.sha256)
    $principal_process_file_full_path = array_distinct($access.principal.process.file.full_path)
    $principal_process_product_specific_process_id = array_distinct($access.principal.process.product_specific_process_id)
    $principal_process_parent_process_product_specific_process_id = array_distinct($access.principal.process.parent_process.product_specific_process_id)
    $target_process_pid = array_distinct($access.target.process.pid)
    $target_process_command_line = array_distinct($access.target.process.command_line)
    $target_process_file_sha256 = array_distinct($access.target.process.file.sha256)
    $target_process_file_full_path = array_distinct($access.target.process.file.full_path)
    $target_process_product_specific_process_id = array_distinct($access.target.process.product_specific_process_id)
    $target_process_parent_process_product_specific_process_id = array_distinct($access.target.process.parent_process.product_specific_process_id)
    $principal_user_userid = array_distinct($access.principal.user.userid)
    $target_user_userid = array_distinct($access.target.user.userid)
    $target_url = array_distinct($access.target.url)

 condition:
    $access and $whois
}