Litecoin core qt wallet hacked - all account balanece lost with one unauthorized transaction

Hi guys! I just found that all my account balance was lost with one unauthorized transaction… there was not much but around 1 LTC was lost. Wallet was not encrypted)(… Please help me to understand what happened - it was some kind of trojan that steal wallets or there is possibility that it was connected with changes in blockchain algorithms)(… Transaction id: 317d429efc1a19556205f0ac777068369533b221d1bfdb58253993b8293fa0db
What can I do now to protect my desktop wallet?

1 LTC lost? or 23.55?

bad clickbait

That is what my wallet gives as transaction details)(…
My balance was 1.03348108 LTC )(…

Probably a wallet trojan, they are common these days but weird though, usually they copy your .dat file and open them elsewhere