Possible Access-Code Validation Beacon to Malware Delivery C2 (via proxy)

ATT&CK techniques

C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1102Web Service
Exfiltration
Impact

What it detects

This rule detects HTTP requests to an /api/submit endpoint carrying a code parameter, the access-code validation call made by a DocuSign-themed loader before it retrieves its second stage in a Vidar delivery chain analyzed by Joe Sandbox. Adversaries gate payload delivery behind server-side code validation to evade sandboxes and analysts, so this submit-with-code request pattern surfaces the loader contacting its delivery infrastructure.

Reporting behind it

Related detections9 linkedT1102 — drag to rearrange

Suspicious Network Connection from mspaint or msiexec (via network_connection)

Possible Discord Webhook C2 or Data Exfiltration

Possible Gamaredon C2 via Ephemeral Tunneling and Worker Services

Possible Gamaredon Dead-Drop C2 via Telegraph and GoFile Web Services

Suspicious APT29 Zulip C2 Communication via curl User-Agent (via proxy)

Possible Telegram API Command and Control DNS Query

Malicious Anubis Ransomware Cloudflare Tunnel via cloudflared (via process_creation)

Possible ITG05 Headlace Staging via Mocky and Mockbin Services (via proxy)

PowerShell Remote Download From Bunny CDN Host

Possible Access-Code Validation Beacon to Malware Delivery C2 (via proxy)

Pivot detection · T1102 · 9 related

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

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →