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Description

The analytic is engineered to detect potential rarely abused malicious filetypes downloaded within a network. They are usually used to spread malwares. Utilizing Splunk search functionality, it examines web proxy logs for blocked actions related to potential threats. Essential data points like the deviceowner, user, urlcategory, url, dest, and filename taken are analyzed to highlight possible malicious endeavors. This detection, marked as an anomaly, aids in early identification and mitigation of malicious download activities, ensuring a safer network environment.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2023-11-21
  • Author: Gowthamaraj Rajendran, Rod Soto, Splunk
  • ID: b0c21379-f4ba-4bac-a958-897e260f964a

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1566 Phishing Initial Access
Kill Chain Phase
  • Delivery
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


1
2
3
4
5



`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`

Macros

The SPL above uses the following Macros:

:information_source: zscaler_potentially_abused_file_download_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • action
  • threatname
  • deviceowner
  • user
  • urlcategory
  • url
  • dest
  • dest_ip
  • action

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.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
8.0 10 80 Potential Abused File Download from dest -[$dest$] on $src$ for user-[$user$].

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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