my friends lost his coins from offline wallet when he was chatting online on facebook messenger
sure he can't restore his coin
so how can protect offline wallet ?
Are you serious with your friend lost coin from offline wallet? I think very safety is you save your coin in offline wallet or using ledger hard ware, no body know hoe to stole coin safe in offline wallet because only your friend have access with hard ware wallet where he saves coin, maybe your friend give hard ware wallet to other people and give data for log in to his wallet.