| Description | This article describes how to block unauthorized connections to IPsec VPN. In some cases, there are unauthorized IPsec VPN connection attempts. By default, they are all blocked by the firewall, but it might be an eyesore to see multiple phase1 negotiation errors on the VPN events, as some of the errors might be negotiation errors for a legitimate VPN connection. In this example the unauthorized remote IP is 192.168.88.152:  |
| Scope | FortiGate. |
| Solution |
 If there is only a list of specific IPs to connect to the IPsec VPN, which in this case is an IPsec site-to-site VPN with a static remote gateway, it is possible to allow only the remote gateway IP and deny all IKE packets with the use of a local-in policy.
 The output after creating the local policy to allow only authorized remote gateways. Unauthorized IP is no longer able to negotiate and is no longer present on the VPN event logs.  Note: This is not applicable for dial-up IPsec VPN peers, as their IP might change and be blocked by the local-in policy. |
FAQs
Technical Tip: How to block unauthorized connections to IPsec VPN? ›
Enable VPN passthrough on routers, crucial for protocols like IPsec. Use access control lists (ACLs) to restrict VPN access to specified IP addresses, enhancing security. Consider placing the VPN server in a Demilitarized Zone (DMZ) for additional isolation from the internal network.
Can IPSec be blocked? ›In some cases, there are unauthorized IPsec VPN connection attempts. By default, they are all blocked by the firewall, but it might be an eyesore to see multiple phase1 negotiation errors on the VPN events, as some of the errors might be negotiation errors for a legitimate VPN connection.
How do I restrict SSL VPN? ›Go to VPN -> SSL-VPN Settings, in 'Restrict Access' select 'Limit access to specific hosts', and add a host to allow for accessing the VPN. Note: If there are SSL VPN authentication rules that have source-address defined as "all", the globally configured source-address will not work.
Can an SSL VPN be blocked? ›There is an option on SSL VPN setting via CLI to enable 'source-address-negate'. It is possible to create a firewall address object (for a blocked IP address), and then use it in the SSL VPN Setting with negate option enabled. This way, FortiGate will only block connection attempts from this address object.
How to limit SSL VPN login attempts and block duration? ›config vpn ssl settings
set login-attempt-limit x <- Insert the number of attempts to allow in place of x. set login-block-time y <- Insert the number of seconds to block attempts for in place of y. The above config will help in preventing brute force attacks through SSL VPN.
The best way to block IPSEC connectivity is to block ESP and not UDP port 500. Most firewalls in the field especially just block UDP 500 in order to avoid IPSEC connectivity. Usually it is a good thing to do as it can block IKE negotiations both for normal scenarios and even when NAT is detected .
How to check if IPsec is blocked? ›Inspect the firewall logs at Status > System Logs, on the Firewall tab. Check for log entries indicating traffic is blocked involving the subnets used in the IPsec tunnel.
How do I block VPN connections? ›There is no universal way to block all VPNs on devices connected to your router. However, you can change your firewall and router settings to block most VPN access, such as creating an access control list to block commonly used VPN communications like UDP port 500.
Which VPN protocol Cannot be blocked? ›OpenVPN is good at providing online anonymity, as it can bypass filters and firewalls, and runs on all major platforms. Privacy — OpenVPN provides excellent anonymity and is compatible with most firewalls. Security — It provides strong encryption and is one of the most secure protocols out there.
Are ISPs allowed to block VPNs? ›Yes, an ISP can block your access to the VPN. While it's not common, an ISP may not like VPNs for allowing you to bypass restrictions the ISP itself has put up. For example, an ISP can block a specific VPN protocol or outright block your VPN connection.
What is the idle timeout for SSL VPN? ›
Your configuration allows a ssl vpn session to remain connected for 10 hours, only if there is NO traffic on that SSL vpn session for 1 hour then the idle timeout would disconnect the session. Any traffic on that SSL vpn will keep it connected until the session hits the session limit of 10 hours.
Is there a limit to the number of VPN connections? ›The number of VPN connections that can be used simultaneously on one account depends on the VPN service provider and the subscription plan you have chosen. Some VPN providers allow only one simultaneous connection per account, while others allow multiple connections.
How do I stop my VPN from timing out? ›- Change VPN tunneling protocol. ...
- Change the VPN server. ...
- Enable obfuscation feature. ...
- Change DNS settings. ...
- Disable the Trusted Network function. ...
- Disable the Multi-Hop feature. ...
- Change the encryption level. ...
- Update your VPN app.
- Go to Network. > IPSec Tunnels and select the tunnel in question.
- Click Enable/Disable at the bottom of the screen.
While IPSec provides robust security for IP communications, its major drawback lies in its complexity and the administrative burden it places on network administrators.
How secure is IPsec? ›IPsec is secure because it adds encryption* and authentication to this process. *Encryption is the process of concealing information by mathematically altering data so that it appears random. In simpler terms, encryption is the use of a "secret code" that only authorized parties can interpret.
Should I disable IPsec? ›Without IPsec Passthrough enabled, your traffic will be blocked if firewall restrictions are in place. This is not an issue if you have a modern router, but it can be an issue if you have an outdated router.