How to tell if my browser/ pc is compromised or my seed phrase?

Ages ago I downloaded some software and it ended up draining my wallet, not fussed as it’s my dev wallet and I only keep like 0.02 eth in there at max but today I went to deploy a contract on one of the wallets on there and when I sent the money from my Binance it transferred it straight away to another wallet, so I tried using another wallet that I already had imported even when I ran the software and that got drained when I sent the money

I ended up deleting MetaMask and creating a whole new seed phrase and that wallet didn’t get drained. So my question is, is my seed phrase only compromised or was it some kind of cookie attack and my browser / computer is and what can I do to combat this