Windows process contacting Dropbox API from non-Dropbox executables

Alerts when a non-Dropbox executable makes initiated connections to Dropbox API endpoints on Windows.

FreeReviewedSigma · High · v2

Product: windows
Category: network_connection
Author: Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2022-04-20
Updated: 2026-07-31

ATT&CK techniques

C2 → Exfiltration

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1105Ingress Tool Transfer
Exfiltration
- T1567.002Exfiltration to Cloud Storage
Impact

What it detects

This rule flags outbound network connections where a process initiates communication to Dropbox API endpoints while the connecting executable is not a Dropbox installation path. Attackers may blend command-and-control or exfiltration traffic into legitimate cloud services like Dropbox to avoid detection. The detection relies on Windows network connection telemetry (initiated flag, destination hostnames ending with api.dropboxapi.com or content.dropboxapi.com) and process image path content to exclude likely legitimate Dropbox clients.

Reporting behind it

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Windows process contacting Dropbox API from non-Dropbox executables

Pivot detection · T1105 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-suspicious-dropbox-api-network-connections-from-non-dropbox-executables-25eabf56

title: Windows process contacting Dropbox API from non-Dropbox executables
id: 5d2faec3-41b8-4cab-92b6-2f9d25815ec9
status: test
description: This rule flags outbound network connections where a process initiates communication to Dropbox API endpoints while the connecting executable is not a Dropbox installation path. Attackers may blend command-and-control or exfiltration traffic into legitimate cloud services like Dropbox to avoid detection. The detection relies on Windows network connection telemetry (initiated flag, destination hostnames ending with api.dropboxapi.com or content.dropboxapi.com) and process image path content to exclude likely legitimate Dropbox clients.
references:
  - https://app.any.run/tasks/7e906adc-9d11-447f-8641-5f40375ecebb
  - https://www.zscaler.com/blogs/security-research/new-espionage-attack-molerats-apt-targeting-users-middle-east
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/network_connection/net_connection_win_domain_dropbox_api.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2022-04-20
tags:
  - attack.command-and-control
  - attack.exfiltration
  - attack.t1105
  - attack.t1567.002
logsource:
  category: network_connection
  product: windows
detection:
  selection:
    Initiated: "true"
    DestinationHostname|endswith:
      - api.dropboxapi.com
      - content.dropboxapi.com
  filter_main_legit_dropbox:
    Image|contains: \Dropbox
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Legitimate use of the API with a tool that the author wasn't aware of
level: high
license: DRL-1.1
related:
  - id: 25eabf56-22f0-4915-a1ed-056b8dae0a68
    type: derived

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