Cisco Secure Firewall - Connection to File Sharing Domain
SPLUNK detection rule by Nasreddine Bencherchali, Splunk · Apache-2.0
The following analytic detects outbound connections to commonly abused file sharing and pastebin-style hosting domains. It leverages Cisco Secure Firewall Threat Defense logs and focuses on allowed connections (action=Allow) where the url field matches a list of known data hosting or temporary storage services. While many of these platforms serve legitimate purposes, they are frequently leveraged by adversaries for malware delivery, data exfiltration, command and control (C2) beacons, or staging of encoded payloads. This analytic is valuable for identifying potential abuse of legitimate infrastructure as part of an attacker's kill chain. If confirmed malicious, this activity may indicate tool staging, credential dumping, or outbound data leaks over HTTP(S).
name: Cisco Secure Firewall - Connection to File Sharing Domain
id: f7e5e792-d907-46c1-a58e-4ff974dc462a
version: 10
creation_date: '2025-04-03'
modification_date: '2026-05-13'
author: Nasreddine Bencherchali, Splunk
status: production
type: Anomaly
description: |
The following analytic detects outbound connections to commonly abused file sharing and pastebin-style hosting domains. It leverages Cisco Secure Firewall Threat Defense logs and focuses on allowed connections (action=Allow) where the url field matches a list of known data hosting or temporary storage services. While many of these platforms serve legitimate purposes, they are frequently leveraged by adversaries for malware delivery, data exfiltration, command and control (C2) beacons, or staging of encoded payloads. This analytic is valuable for identifying potential abuse of legitimate infrastructure as part of an attacker's kill chain. If confirmed malicious, this activity may indicate tool staging, credential dumping, or outbound data leaks over HTTP(S).
data_source:
- Cisco Secure Firewall Threat Defense Connection Event
search: |
`cisco_secure_firewall` action IN ("Trust", "Allow", "allowed") EventType=ConnectionEvent url IN ("*//objects.githubusercontent.com*", "*anonfiles.com*", "*cdn.discordapp.com*", "*ddns.net*", "*dl.dropboxusercontent.com*", "*ghostbin.co*", "*glitch.me*", "*gofile.io*", "*hastebin.com*", "*mediafire.com*", "*mega.nz*", "*onrender.com*", "*pages.dev*", "*paste.ee*", "*pastebin.com*", "*pastebin.pl*", "*pastetext.net*", "*privatlab.com*", "*privatlab.net*", "*send.exploit.in*", "*sendspace.com*", "*storage.googleapis.com*", "*storjshare.io*", "*supabase.co*", "*temp.sh*", "*transfer.sh*", "*trycloudflare.com*", "*ufile.io*", "*w3spaces.com*", "*workers.dev*")
| stats count min(_time) as firstTime max(_time) as lastTime
Values(src_port) as src_port
Values(dest) as dest
Values(dest_port) as dest_port
Values(rule) as rule
Values(url) as url
Values(EVE_Process) as EVE_Process
by src, transport, action
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `cisco_secure_firewall___connection_to_file_sharing_domain_filter`
how_to_implement: |
This search requires Cisco Secure Firewall Threat Defense Logs, which
includes the ConnectionEvent 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 access policy must also enable logging.
known_false_positives: |
Legitimate users and applications may use these domains for benign purposes such as file transfers, collaborative development, or storing public content.
Developer tools, browser extensions, or open-source software may connect to githubusercontent.com or cdn.discordapp.com as part of normal operation.
It is recommended to review the associated process (`EVE_Process`), user behavior, and frequency of access before classifying the activity as suspicious.
references:
- https://www.cisco.com/c/en/us/td/docs/security/firepower/741/api/FQE/secure_firewall_estreamer_fqe_guide_740.pdf
drilldown_searches:
- name: View the detection results for - "$src$"
search: '%original_detection_search% | search src = "$src$"'
earliest_offset: $info_min_time$
latest_offset: $info_max_time$
- name: View risk events for the last 7 days for - "$src$"
search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src$") | 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: The host $src$ initiated a connection to the file sharing or pastebin domain $url$.
threat_objects:
- field: url
type: url
analytic_story:
- Cisco Secure Firewall Threat Defense Analytics
- Scattered Lapsus$ Hunters
asset_type: Network
mitre_attack_id:
- T1071.001
- T1090.002
- T1105
- T1567.002
- T1588.002
product:
- Splunk Enterprise
- Splunk Enterprise Security
- Splunk Cloud
category: network
security_domain: network
tests:
- name: True Positive Test
attack_data:
- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/cisco_secure_firewall_threat_defense/connection_event/connection_events.log
source: not_applicable
sourcetype: cisco:sfw:estreamer
test_type: unit
CIRCL