Fortinet Updated NSE4_FGT_AD-7.6 Exam Questions and Answers by hawa

“ Rate-based IPS signatures also allows you to detect anomalies, which are unusual behaviors in the network...”

“There are two ways to add predefined signatures to an IPS sensor. One way is to select the signatures individually... The second way to add a signature to a sensor is using filters.”

“ You can also add rate-based signatures to block specific traffic when the threshold is exceeded. On the CLI, If you set the command rate-mode to periodical, FortiGate triggers the action when the threshold is reached during the configured Duration time period. ”

Technical Deep Dive:

The correct answer is C. Use IPS signatures, rate-mode periodical option.

The guide is explicit that this behavior belongs to rate-based IPS signatures . The question asks for blocking traffic when a signature is triggered a certain number of times within a defined interval. That is exactly what rate-mode periodical does: it evaluates the trigger count over the configured duration window and then applies the configured IPS action when the threshold is met.

Why the other options are wrong:

A is wrong because rate-mode 60 is not the documented syntax or method.

B is wrong because packet logging records packets; it does not implement threshold-based blocking logic.

D is wrong because the guide ties rate-mode periodical to rate-based signatures , not to IPS filters as the mechanism for this threshold behavior.

Operationally, this is used for anomaly-style detection, similar in concept to lightweight rate-based protection. A typical CLI pattern is along these lines:

config ips sensor

edit " custom-ips "

config entries

edit 1

set rule < signature_id >

set rate-mode periodical

set rate-count < threshold >

set rate-duration < seconds >

set action block

next

end

next

end

This works best when applied only to relevant protocols and signatures, because broad use of rate-based signatures can consume more resources and increase false-positive risk.

“You can configure the fail-open setting under config ips global to control how the IPS engine behaves when the IPS socket buffer is full .”

“If the IPS engine does not have enough memory to build more sessions , the fail-open setting determines whether the FortiGate should drop the sessions or bypass the sessions without inspection .”

“It is important to understand that the IPS fail-open setting is not just for conserve mode—it kicks in whenever IPS fails. Most failures are due to a high CPU issue or a high memory (conserve mode) issue.”

Technical Deep Dive:

The correct answer is A .

The log text says:

logdesc= " IPS session scan paused "

action= " drop "

msg= " IPS session scan, enter fail open mode "

That combination indicates an IPS failure condition , specifically the condition described in the guide where the IPS socket buffer is full and the IPS engine lacks enough memory/resources to build additional sessions. In that state, FortiGate applies the configured IPS fail-open behavior . Since the log shows action= " drop " , the device is not bypassing those new sessions; it is dropping them.

Why the other choices are wrong:

B is wrong because the guide ties fail-open to socket buffer/resource exhaustion , not packet decode failure.

C is wrong because this is not evidence of a manual diagnostic pause.

D is wrong because the study guide does not associate this log with dirty-flag packet reevaluation.

Operationally, this usually points to high memory , high CPU , or conserve-mode pressure affecting the IPS engine. Useful checks are:

get system performance status

diagnose hardware sysinfo conserve

diagnose sys top

Those help confirm whether the IPS issue is being driven by memory pressure or CPU exhaustion.

“The only security features you can apply using SSL certificate inspection mode are web filtering and application control... certificate inspection does not allow FortiGate to inspect the flow of encrypted data.”

“For antivirus or IPS control, you should use a deep-inspection profile.”

“Within the full SSL inspection profile, you can also specify which SSL sites, if any, you want to exempt from SSL inspection.”

Technical Deep Dive:

The correct answers are A and B .

A is correct because if the firewall policy uses certificate inspection , FortiGate can inspect certificate/SNI metadata only. It cannot decrypt the HTTPS payload, so the antivirus engine never sees the EICAR file contents. That means HTTPS malware scanning fails even though HTTP scanning works.

B is also correct because if the destination site is exempt from SSL inspection , FortiGate intentionally skips decryption for that HTTPS session. Again, no payload decryption means no antivirus content scan.

Why the others are wrong:

C is not the likely reason here, especially for EICAR, which is a very small test file.

D would usually cause browser certificate warnings or connection issues during deep inspection, not a clean download that bypasses AV inspection.

Operationally, HTTPS antivirus requires this chain to be true:

firewall policy match → SSL deep inspection active → site not exempted → AV profile applied .

If either certificate-inspection is used or the site is exempted, FortiGate cannot inspect the encrypted file body.