Containing Crytox ransomware after FortiGate SSL‑VPN abuse at a Singapore‑based entertainment equipment distributor (December 2024)
At a glance
- Customer: Singapore‑based entertainment equipment distributor
- Environment: FortiGate SSL‑VPN, virtualised Windows servers (17 VMs across 3 physical hosts), Active Directory running as a VM
- Attack type: Ransomware intrusion and encryption (Crytox)
- Initial vector (assessed): FortiGate SSL‑VPN access abuse (credential compromise and/or exploitation; weak password hygiene noted)
- Blackpanda services: DFIR investigation, containment guidance, EDR deployment, threat monitoring, VPN hardening recommendations
CHALLENGE
Ransomware discovered mid‑incident in a virtualised environment
The distributor learned of the attack after systems began failing during routine remote support and a ransom note was identified. The environment complexity increased response pressure:
- Multiple VMs hosted across physical servers
- Active Directory operating as a VM
- Limited central visibility because many systems were not domain‑joined
VPN edge exposure and weak authentication raised the likelihood of repeat compromise
Blackpanda identified confirmed malicious access via the FortiGate firewall where the attacker logged in successfully via SSL‑VPN using a privileged account from overseas IPs, with multiple VPN sessions over the intrusion window. The firewall firmware was also assessed as older and past engineering support, increasing exposure to known exploited vulnerabilities.
SOLUTION
1. Immediate containment actions to stop further attacker access
Blackpanda advised and supported containment measures including:
- Temporarily disabling SSL‑VPN
- Resetting SSL‑VPN passwords
- Enforcing MFA for VPN connections
- Resetting compromised admin accounts
- Deploying Checkpoint EDR for visibility and monitoring
2. Reconstructing the intrusion timeline from firewall logs and endpoint evidence
Blackpanda confirmed:
- The attacker’s access window spanned several hours on 21 Dec 2024, with multiple VPN sessions.
- Encryption activity appeared to be executed manually across servers (distinct start times; no evidence of GPO/script-based mass deployment).
3. Data exfiltration assessment and ongoing monitoring
Blackpanda found no evidence of data exfiltration attempts during the observed compromise window and no evidence of further unauthorised access after initial containment actions.
RESULTS
1. Attacker access was cut off and visibility restored
Containment actions (VPN shutdown, password resets, MFA enforcement, EDR deployment) removed the attacker’s access path and restored detection capability across surviving systems.
2. Encryption impact was confirmed and characterised
Blackpanda confirmed Crytox ransomware execution and documented encryption characteristics such as the “.wait” extension and ransom note behavior, helping the client align recovery steps to the actual variant.
3. No evidence of data exfiltration in the reviewed window
Blackpanda found no evidence of data being targeted or transferred for exfiltration during the compromise window.
4. A clear hardening roadmap for VPN and identity posture
Key recommendations included improved password management, firewall hardening, removing unused accounts, enforcing MFA on VPN accounts, and engaging MDR to reduce dwell time in future incidents.
FAQ: Crytox Ransomware and FortiGate VPN Intrusions
Q1. How did the attacker likely get in?
Evidence shows successful SSL‑VPN logins via a privileged account from overseas IPs. The most likely paths are credential compromise (including password guessing) and/or exploitation of exposed vulnerabilities on older firewall firmware.
Q2. Why does VPN MFA matter so much?
If credentials are leaked or guessed, MFA can block access and prevent the attacker from establishing a remote foothold.
Q3. Was data stolen?
Blackpanda found no evidence of data exfiltration attempts during the observed window.
Q4. Why was the ransomware execution assessed as manual?
Encryption start times differed across servers and there was no evidence of GPO, scripted rollout, or scheduled-task deployment — consistent with manual execution per server.
Q5. What are the most important controls to prevent a repeat?
Harden VPN access (MFA, remove unused accounts, strong passwords), keep firewall firmware supported and patched, and ensure continuous endpoint visibility via EDR/MDR.
What this means for you
Ransomware doesn’t always begin with email — it often begins at the edge, where VPN and firewall controls decide whether an attacker gets a foothold. If your environment runs critical services on virtual infrastructure, rapid containment and restored visibility are the difference between a contained incident and extended operational shutdown.
