@audax10 said in Suricata blocking google.com:
As far as I understand, Legacy Mode blocks the host, while Inline blocks (drop/reject) the triggered rules. This is a big difference. I noticed that Google Maps connects to the same host as "ET INFO Android Device Connectivity Check" rule. So when the host is blocked rather than the rule specification, we will probably block more than we need. Is it correct @bmeeks ?
Yes, Inline IPS Mode is much more selective as it drops individual packets instead of entirely blocking a host by its IP address. However, when using Inline IPS Mode, you must change the action of rules that you wish to block traffic from ALERT to DROP. Otherwise, they will just generate alerts and not drop or block the traffic. Rule actions are default set to ALERT. In Legacy Mode, any alert is interpreted as a block. But that is NOT the case when using Inline IPS Mode. In that mode rule actions are interpreted literally! So if the action is ALERT, that's all that happens. To block traffic in Inline IPS Mode, the rule action must be changed to DROP.
Changing to Inline IPS Mode without also changing rule actions via SID MGMT or some other means will result in nothing being blocked.
The easiest way to manage this is to use the SID MGMT tab features. You can also alter the action of individual rules on the RULES tab and on the ALERTS tab once Inline IPS Mode is enabled. If you are new to this, you should read through this long Sticky Post first: https://forum.netgate.com/topic/143812/snort-package-4-0-inline-ips-mode-introduction-and-configuration-instructions. While a little of the information in that thread is probably dated by now, the majority of it is still applicable.