I’m thinking it’s probably easiest to do this at the router.

or Outpost Firewall 1.0.242

If you are behind a home gateway router, you should be safe from non host initiated incoming Internet traffic .

As for outgoing Internet traffic, setting a bogus gateway will ensure nothing gets out beyond your local network .
For example, if your normal gateway is 192.168.0.1 , setting it to 192.168.0.254 on the Windows 98 machine will ensure that it only has access to your local network .

I was going to suggest similar to darry: delete the machine's gateway setting. No gateway means no way to the internet.

Or you could set up a local DNS cache (unbound or such) combined with a filter list on your server, to allow only safe sites to be accessed.
If you do this, you can also set up the firewall specifically for your obsolete-OS systems so that they can only access the most necessary ports.

dragonkn wrote:

Hi:)
It's a little danger to have internet on that old machine i think.

Quite the opposite; it's probably the safest machine to connect to the net; none of the modern malware will work on it (nor will most of the internet, for that matter). 🤣

dragonkn wrote:

Can i block internet on this old pc somehow? Thanks

I support the suggestions to just delete/change the default gateway. Easy to do, easy to undo, in case you suddenly want to get outside access.

Many thanks for answers!
Now , i dont have internet on old machine:)

I don't bother with anti-malware or antivirus on my 9x machines. If I get a virus I don't care, it's not my main computer, no other Windows computers on the network it could infect, besides that as was stated above no modern malware will run on it anyway.

Just don't try any shady downloads (if they would even load...) and you'll be fine.

Block the Win98 computers network card's MAC address on any WAN/Internet access on your router as well, if you have that option. I have had routers that have a list, in were you can block access on MAC-adress level.