Zscaler Malware Activity Threat Blocked

SPLUNK detection rule by Rod Soto, Gowthamaraj Rajendran, Splunk · Apache-2.0

The following analytic identifies potential malware activities within a network that are blocked by Zscaler. It leverages web proxy logs to filter for blocked actions associated with malware, aggregating occurrences by user, URL, and threat category. This detection is significant for SOC as it highlights attempts to access malicious content, indicating potential compromise or targeted attacks. If confirmed malicious, this activity could signify an ongoing attempt to infiltrate the network, necessitating immediate investigation to prevent further threats and ensure network integrity.

name: Zscaler Malware Activity Threat Blocked
id: ae874ad8-e353-40a7-87d4-420cdfb27d1a
version: 10
creation_date: '2024-04-17'
modification_date: '2026-05-13'
author: Rod Soto, Gowthamaraj Rajendran, Splunk
status: production
type: Anomaly
description: The following analytic identifies potential malware activities within a network that are blocked by Zscaler. It leverages web proxy logs to filter for blocked actions associated with malware, aggregating occurrences by user, URL, and threat category. This detection is significant for SOC as it highlights attempts to access malicious content, indicating potential compromise or targeted attacks. If confirmed malicious, this activity could signify an ongoing attempt to infiltrate the network, necessitating immediate investigation to prevent further threats and ensure network integrity.
data_source: []
search: |-
    `zscaler_proxy` action=blocked threatname=*malware* threatcategory!=None
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY action deviceowner user
           urlcategory url src
           dest
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `zscaler_malware_activity_threat_blocked_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 Zscalar 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 ("$src$", "$user$") | 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: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: src
          type: system
          score: 20
          message: Potential Malware Activity from dest -[$dest$] on $src$ for user-[$user$].
        - field: user
          type: user
          score: 20
          message: Potential Malware Activity from dest -[$dest$] on $src$ for user-[$user$].
threat_objects:
    - field: url
      type: url
analytic_story:
    - Zscaler Browser Proxy Threats
asset_type: Web Server
mitre_attack_id:
    - T1566
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: web
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
      test_type: unit

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