thanks i think ...
I use Microsoft AV and their Firewall. I'm researching alternatives now.
The download was scanned, though all future d/l's will be looked at in sandboxie.
So, assuming my wallet.dat keys have been obtained, any future deposits/transactions to this address are compromised. Is there anything I can do? If I uninstall & remove all references to litecoin on this PC will that be enough to then re-install?
Have the coins actually gone, despite what my wallet reports? Is there any chance of getting them back?
Anything that Microsoft makes is garbage. I recommend using Bitdefender. If all your coins have been already compromised, there is nothing you can to retrieve them.
If you have 0 coins in your wallet and trade sites, delete every trace of every wallet and start over. From wallet.dat, blockchains, wallet-qt... everything. Scan your computer with the new anti-virus/firewall program.
Configure your firewall to maximum security.
Start over. Remember, the best place for digital currency is on a device that rarely or never gets connected to the internet, an old PC or whatever.
Be cautious on what you download and what enters your PC
Goodluck