zscaler_potentially_abused_file_download.yml

name: Zscaler Potentially Abused File Download
id: b0c21379-f4ba-4bac-a958-897e260f964a
version: 5
date: '2024-11-15'
author: Gowthamaraj Rajendran, Rod Soto, Splunk
status: production
type: Anomaly
data_source: []
description: The following analytic identifies the download of potentially malicious
  file types, such as .scr, .dll, .bat, and .lnk, within a network. It leverages web
  proxy logs from Zscaler, focusing on blocked actions and analyzing fields like deviceowner,
  user, urlcategory, url, dest, and filename. This activity is significant as these
  file types are often used to spread malware, posing a threat to network security.
  If confirmed malicious, this activity could lead to malware execution, data compromise,
  or further network infiltration.
search: '`zscaler_proxy` url IN ("*.scr", "*.dll", "*.bat", "*.lnk") | stats count
  min(_time) as firstTime max(_time) as lastTime by deviceowner user urlcategory url
  src filename dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`
  | `zscaler_potentially_abused_file_download_filter`'
how_to_implement: You must install the latest version of Zscaler Add-on from Splunkbase.
  You must be ingesting Zscaler events into your Splunk environment through an ingester.
  This analytic was written to be used with the "zscalernss-web" sourcetype leveraging
  the Zscaler proxy data. This enables the integration with Splunk Enterprise Security.
  Security teams are encouraged to adjust the detection parameters, ensuring the detection
  is tailored to their specific environment.
known_false_positives: False positives are limited to Zscaler configuration.
references:
- https://help.zscaler.com/zia/nss-feed-output-format-web-logs
drilldown_searches:
- name: View the detection results for - "$src$" and "$user$"
  search: '%original_detection_search% | search  src = "$src$" user = "$user$"'
  earliest_offset: $info_min_time$
  latest_offset: $info_max_time$
- name: View risk events for the last 7 days for - "$src$" and "$user$"
  search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src$",
    "$user$") starthoursago=168  | stats count min(_time) as firstTime max(_time)
    as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk
    Message" values(analyticstories) as "Analytic Stories" values(annotations._all)
    as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics"
    by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
  earliest_offset: $info_min_time$
  latest_offset: $info_max_time$
rba:
  message: Potential Abused File Download from dest -[$dest$] on $src$ for user-[$user$].
  risk_objects:
  - field: src
    type: system
    score: 8
  - field: user
    type: user
    score: 8
  threat_objects:
  - field: url
    type: url
tags:
  analytic_story:
  - Zscaler Browser Proxy Threats
  asset_type: Web Server
  mitre_attack_id:
  - T1566
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  security_domain: threat
tests:
- name: True Positive Test
  attack_data:
  - data: 
      https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1566/zscalar_web_proxy/zscalar_web_proxy.json
    source: zscaler
    sourcetype: zscalernss-web