Sophos Firewall reported computer not sending heartbeat signals

Are you able to see any similar errors in the logs located at "C:\ProgramData\Sophos\Heartbeat\Logs"? 

Could the device be entering a hibernate or sleep state at the times when these events are generated?

I was on the computer and it was in standby.

I could see the Intel Networkdriver was frequently dumping something all the time during standby.

Netwtw10
7026
7026 - Dump after return from D3 after cmd

Netwtw10
7025
7025 - Dump after return from D3 before cmd

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Probably causing network flapping which triggers Heartbeat Change.

In the heartbeat log I could see many, many events during standby mode: network has changed - firewall may disconnect

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2022-11-16T09:21:38.596Z [ 5212: 6340] A Sending network status
2022-11-16T09:21:38.596Z [ 5212: 6340] A The network status has changed, the Firewall may disconnect.
2022-11-16T09:21:38.598Z [ 5212: 6340] A Connection closed (network error).

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I updated (network) drivers and BIOS at first place and will monitor the situation.

Can the heartbeat module be tweaked so that it is compatible with Standby?

Everyone taks about saving energy - would be non-pc to disable standby for heartbeat to work.

I was able to get some additional feedback on this from our team. 

The decision-making process behind when these alerts are generated will take place entirely on the firewall. Only if network traffic continues to be routed to the firewall without heartbeat traffic periodically, will the alert be generated.

Do you know if the NIC on the affected device remains active/communicating on the network while the system is in hibernate mode? What could also help is checking the power saver settings in Device Manager to check if the NIC is configured to stop communicating when the device enters a sleep state.

There are a couple of options available from the XG Console which can limit the frequency at which these alerts/events are generated in Sophos Central. I will follow up with you via PM to share these.

Hi Qoosh  and thanks for your message.

The NICs, LAN or WiFi, may be shot down by the OS to save energy. That option is not disabled.

As written earlier, it looks to me like the NIC driver does some usless behaviour / dumping something that shows with those Netwtw10 Events every few seconds. That probably wakes the NIC, sends some packets the firewall sees when the heartbeat driver already sent info to the firewall, that the device is now off.

After the driver and BIOS updates, the issue has not happened to the computer that was most frequent before. Probably Intel / Fujitsu changed something on the network behaviour in Hibernate.

Will continue to monitor the behaviour on our side.

Interestingly the events almost stopped completely after Nov 16th.

Hi Qoosh  and thanks for your message.

The NICs, LAN or WiFi, may be shot down by the OS to save energy. That option is not disabled.

As written earlier, it looks to me like the NIC driver does some usless behaviour / dumping something that shows with those Netwtw10 Events every few seconds. That probably wakes the NIC, sends some packets the firewall sees when the heartbeat driver already sent info to the firewall, that the device is now off.

After the driver and BIOS updates, the issue has not happened to the computer that was most frequent before. Probably Intel / Fujitsu changed something on the network behaviour in Hibernate.

Will continue to monitor the behaviour on our side.

Interestingly the events almost stopped completely after Nov 16th.

Thanks for following up with us here. Hopefully, this will provide some further insight for others that may encounter similar issues or have these same concerns.