Detect Portscan on ASA Outside Interface in FirePower

[markus.bock]

Hello,

we have running asa 5525-X with firepower module. I have enable Portscan detection in IPS rule and I can see portscans from internal hosts to ip adresses in the www

But when I do a portscan from a host in the internet to a extenal ip on the outside interface of the ASA the portscan is not detected.

How can I achieve this?

THANKS