Fortinet VPN Credential Stuffing Attacks
In 2021, multiple organizations reported breaches resulting from credential stuffing attacks targeting Fortinet VPN appliances. Attackers used previously leaked username and password combinations to gain unauthorized access to corporate networks, bypassing multi-factor authentication in some cases.
Credential stuffing is a type of brute-force attack where attackers use automated tools to try large numbers of username/password pairs, often obtained from previous data breaches. If users reuse passwords across services, attackers can gain access to sensitive systems with minimal effort.
Technical Details
Attackers targeted Fortinet VPN endpoints exposed to the internet. By automating login attempts with known credentials, they were able to access internal networks, steal data, and deploy additional malware. In some cases, attackers exploited unpatched vulnerabilities in the VPN software to escalate privileges or bypass authentication controls.
Proof of Concept
A typical credential stuffing script might look like this:
import requests
url = "https://vpn.example.com/remote/login"
credentials = [
("user1", "password1"),
("user2", "password2"),
# ... more credentials ...
]
for username, password in credentials:
resp = requests.post(url, data={"username": username, "password": password})
if "Welcome" in resp.text:
print(f"Valid credentials: {username}:{password}")
Real-World Impact
Successful credential stuffing attacks on Fortinet VPNs led to data breaches, ransomware deployments, and lateral movement within victim networks. Organizations faced regulatory fines, reputational damage, and operational disruptions.
Lessons Learned
The Fortinet incidents highlight the importance of enforcing strong password policies, enabling multi-factor authentication, and monitoring for suspicious login activity. Organizations should regularly audit VPN access logs, disable unused accounts, and educate users about the risks of password reuse.