VT Relationships File Contacts Tor IP

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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 vt_relationships_file_contacts_tor_ip {

  meta:
    author = "Google Cloud Security"
    description = "Alert on known Hash contacting Tor IP with VT Relationships."
    rule_id = "mr_a6f8b114-8fdb-4f39-8820-8961dcbb1079"
    rule_name = "VT Relationships File Contacts Tor IP"
    tactic = "TA0011"
    technique = "T1090.003"
    type = "alert"
    tags = "vt, tor"
    data_source = "microsoft defender atp"
    severity = "Critical"
    priority = "High"

  events:
    $network.metadata.event_type = "NETWORK_CONNECTION"
    $network.principal.process.file.sha256 = $file_hash
    $network.target.ip = $ip
    $network.principal.hostname = $hostname

    // Uses VirusTotal integration via entity graph, this section maps to principal process file hash
    $vt.graph.metadata.entity_type = "FILE"
    $vt.graph.metadata.source_type = "GLOBAL_CONTEXT"
    $vt.graph.metadata.vendor_name = "VirusTotal"
    $vt.graph.metadata.product_name = "VirusTotal Relationships"
    $vt.graph.entity.file.sha256 = $file_hash

    // Uses VirusTotal integration via entity graph, this section maps the hash to the ip address it contacts
    $vt.graph.relations.entity_type = "IP_ADDRESS"
    $vt.graph.relations.relationship = "CONTACTS"
    $vt.graph.relations.entity.ip = $ip

    // Tor IP listing provided by GCTI Feed
    $gcti.graph.entity.artifact.ip = $ip
    $gcti.graph.metadata.entity_type = "IP_ADDRESS"
    $gcti.graph.metadata.source_type = "GLOBAL_CONTEXT"
    $gcti.graph.metadata.threat.threat_feed_name = "Tor Exit Nodes"
    $gcti.graph.metadata.vendor_name = "Google Cloud Threat Intelligence"
    $gcti.graph.metadata.product_name = "GCTI Feed"

  match:
    $hostname over 5m

  outcome:
    $risk_score = max(
        if($gcti.graph.metadata.threat.confidence = "HIGH_CONFIDENCE", 70) +
        // Unauthorized target geographies
        if($network.target.ip_geo_artifact.location.country_or_region = "Cuba", 20) +
        if($network.target.ip_geo_artifact.location.country_or_region = "Iran", 20) +
        if($network.target.ip_geo_artifact.location.country_or_region = "North Korea", 20) +
        if($network.target.ip_geo_artifact.location.country_or_region = "Russia", 20) +
        if($network.target.ip_geo_artifact.location.country_or_region = "Syria", 20)
    )
    $event_count = count_distinct($network.metadata.id)
    $count_file_hash = count_distinct($file_hash)
    $count_tor_ips = count_distinct($ip)
    $tor_geoip_country = array_distinct($network.target.ip_geo_artifact.location.country_or_region)
    $tor_geoip_state = array_distinct($network.target.ip_geo_artifact.location.state)
    // added to populate alert graph with additional context
    $principal_ip = array_distinct($network.principal.ip)
    $target_ip = array_distinct($network.target.ip)
    $principal_process_pid = array_distinct($network.principal.process.pid)
    $principal_process_command_line = array_distinct($network.principal.process.command_line)
    $principal_process_file_sha256 = array_distinct($network.principal.process.file.sha256)
    $principal_process_file_full_path = array_distinct($network.principal.process.file.full_path)
    $principal_process_product_specific_process_id = array_distinct($network.principal.process.product_specific_process_id)
    $principal_process_parent_process_product_specific_process_id = array_distinct($network.principal.process.parent_process.product_specific_process_id)
    //$target_process_pid = array_distinct($network.target.process.pid)
    //$target_process_command_line = array_distinct($network.target.process.command_line)
    //$target_process_file_sha256 = array_distinct($network.target.process.file.sha256)
    $target_process_file_full_path = array_distinct($network.target.process.file.full_path)
    //$target_process_product_specific_process_id = array_distinct($network.target.process.product_specific_process_id)
    //$target_process_parent_process_product_specific_process_id = array_distinct($network.target.process.parent_process.product_specific_process_id)
    $principal_user_userid = array_distinct($network.principal.user.userid)
    //$target_user_userid = array_distinct($network.target.user.userid)
    $target_url = array_distinct($network.target.url)

  condition:
    $network and $vt and $gcti
}