Detection: Cisco Secure Firewall - Binary File Type Download

Updated Date: 2025-04-03 ID: 24b2c2e3-2ff7-4a23-b814-87f8a62028cd Author: Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects file downloads involving executable, archive, or scripting-related file types that are commonly used in malware delivery. These file types include formats like PE executables, shell scripts, autorun files, installers, and known testing samples such as EICAR. This detection leverages Cisco Secure Firewall Threat Defense logs and enriches the results using a filetype lookup to provide context. If confirmed malicious, these downloads could indicate the initial infection vector, malware staging, or scripting abuse.

 1`cisco_secure_firewall` EventType=FileEvent FileDirection="Download" 
 2FileType IN ("ISHIELD_MSI", "BINHEX", "BINARY_DATA", "ELF", "MACHO", "JARPACK", "TORRENT", "AUTORUN", "EICAR", "LNK", "SCR", "UNIX_SCRIPT")
 3
 4| lookup cisco_secure_firewall_filetype_lookup Name as FileType OUTPUT Description
 5
 6| stats count min(_time) as firstTime max(_time) as lastTime
 7        values(uri) as uri
 8        values(ClientApplication) as ClientApplication
 9        values(file_hash) as file_hash
10        values(SHA_Disposition) as SHA_Disposition
11        by FileDirection FileType src_ip dest app file_name ThreatName dest_port Description
12
13| `security_content_ctime(firstTime)`
14
15| `security_content_ctime(lastTime)`
16
17| table firstTime lastTime src_ip dest dest_port FileDirection FileType Description uri file_name file_hash app ClientApplication SHA_Disposition ThreatName
18
19| `cisco_secure_firewall___binary_file_type_download_filter`

Data Source

Name Platform Sourcetype Source
Cisco Secure Firewall Threat Defense File Event N/A 'cisco:sfw:estreamer' 'not_applicable'

Macros Used

Name Value
cisco_secure_firewall sourcetype="cisco:sfw:estreamer"
cisco_secure_firewall___binary_file_type_download_filter search *
cisco_secure_firewall___binary_file_type_download_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1203 Exploitation for Client Execution Execution
T1059 Command and Scripting Interpreter Execution
Installation
DE.AE
CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

This search requires Cisco Secure Firewall Threat Defense Logs, which includes the FileEvent EventType. This search uses an input macro named cisco_secure_firewall. We strongly recommend that you specify your environment-specific configurations (index, source, sourcetype, etc.) for Cisco Secure Firewall Threat Defense logs. Replace the macro definition with configurations for your Splunk environment. The search also uses a post-filter macro designed to filter out known false positives. The logs are to be ingested using the Splunk Add-on for Cisco Security Cloud (https://splunkbase.splunk.com/app/7404). The malware & file access policy must also enable logging.

Known False Positives

IT admins or developers may legitimately download executables or scripts as part of their normal workflow. Apply additional filters accordingly.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

The host $src_ip$ downloaded a file $file_name$ of type $FileType$ from $dest$.

Risk Object Risk Object Type Risk Score Threat Objects
src_ip system 30 file_hash, file_name

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset not_applicable cisco:sfw:estreamer
Integration ✅ Passing Dataset not_applicable cisco:sfw:estreamer

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

Source: GitHub | Version: 1