Are a firewall and antivirus necessary in Kubuntu?

[greenster]

I'm keen to hear your thoughts...

Should I use a firewall and antivirus in Kubuntu?

At the moment, I'm not using either.

Is that risky?

[skyfishgoo]

as long as your router is set up properly you should not need a firewall on your device.

there is no AV software for linux, you have ad blockers for browsers and you avoid installing code from unknown sources (still to your distro's official repositories).

[Snowhog]

there is no AV software for linux

That isn't true.

[Qqmike]

Most of us do not even think about this -- and haven't thought about it.
But your question is good. We'll let the AV experts chime in.
Personally ...
I have never done anything to protect my system. Been here since 2007 on Kubuntu (and other distros as experiments).
--> Except to be careful of weird stuff, careful about clicking on links in emails, etc.

You might search and study this topic: NAT routers.
Most of us are behind a NAT router these days.

EDIT: Oops ... Malwarebytes doesn't seem to offer anything for Linux like they used to (except perhaps commercial versions?).

You might be aware of the FREE versions of Malwarebytes -- just in case you might want to conduct a scan of your system.
I personally see no need to subscribe to the non-free (the priced) versions.

https://www.malwarebytes.com/solutions/virus-scanner

https://www.malwarebytes.com/solutions/free-antivirus

Maybe look at ClamAV.

I don't think you really need to worry, though.