We use an external scanner (Qualys) to scan our external assets. We have a firewall in front of the external assets, but it is configured to whitelist the scanner so that the external assets get scanned in-depth. But the firewall is also configured to drop incoming ICMP timestamp requests, which the scanner is still able to send and get a timestamp request from the external assets behind the firewall.

We have consulted with the vendor, vendor conducted some scans and analysis on their end and replied the target response cannot be controlled by Qualys scan. The ICMP timestamp is an active QID means it is only flagged based on the target response. And yes, I can see the timestamp response with the actual timestamp replies for the scanned assets. So I am just wondering whether I am missing something here. Apologies in advance if it seems to be a silly question to ask :) Any guidance would be much appreciated.

1 Answer 1


The answer depends on the way the whitelist is implemented on the firewall.

Is the source IP of the Scanner whitelisted, then this will take precedence to the ICMP drop.

I would recommend checking the order of the firewall rules and if the the whitelist rule comes before the drop rule.

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