How To Bypass Fortiguard Intrusion - Prevention - Access Blocked Fixed

: For HTTPS traffic, whitelisting a URL may not be sufficient in certain scenarios. FortiGate's web filter evaluates the effective hostname using both the SNI (Server Name Indication) and the CN/SAN from the SSL certificate. If these don't match the URL you've whitelisted, the block may still occur. This explains why some web filter exemptions appear to fail despite correct configuration.

Independent testing by NSS Labs found that both Palo Alto and Fortinet firewalls could be bypassed using Layer 4 TCP evasions, demonstrating that IPS systems at this level may have inherent limitations.

What is the specific or Error Message shown in the FortiGate logs?

In your browser settings (Chrome/Firefox), search for "Secure DNS" and set it to a provider like Cloudflare ( ) or Google ( 4. Utilize Mobile Hotspot/Data : For HTTPS traffic, whitelisting a URL may

Fortiguard uses categories to filter web content. Lifestyle and Entertainment is one such category that might block access to certain websites.

When a legitimate user or penetration tester encounters an "Access Blocked" message due to an IPS trigger, it is usually because the traffic closely resembles a signature pattern or violates an established protocol rule. Common Methods to Bypass FortiGuard IPS

IPS looks for deviations from standard protocol specifications (e.g., malformed HTTP headers or unusual TCP flags). This explains why some web filter exemptions appear

Converting scripts or payloads into standard Base64 strings.

When legitimate traffic is blocked by FortiGuard IPS, "bypassing" the system should never mean disabling security entirely. Instead, administrators use controlled, policy-based adjustments to restore access without exposing the network to risk. 1. Identify the Triggering Signature

Remember that network security exists for a reason, and bypassing it may expose you or your organization to real threats that FortiGuard is designed to prevent. Advanced Protocol Fragmentation

To understand how blocks are bypassed, you must first understand how FortiGuard inspects traffic. Unlike simple URL filters that look only at web addresses, FortiGuard IPS performs Deep Packet Inspection (DPI).

If the block is happening at the DNS level (the system that turns "google.com" into an IP address), changing your device’s DNS settings to a public provider like Google (8.8.8.8) or Cloudflare (1.1.1.1) can sometimes circumvent simple web filtering [1]. To give you the most helpful advice, could you let me know:

When a penetration tester encounters a block, the goal is to alter the signature or delivery method of the traffic so the IPS no longer recognizes it as a threat, while still ensuring the payload executes correctly on the target machine. 1. Advanced Protocol Fragmentation