Coins change on a day to day basis https://whattomine.com/
You cant attack the chain really, you culd possebly make a worm that atacks nodes to bring them down but that would not do much. Maby a worm that atacks miners and changes blocks but need to infect over 51% of the miners out there to harm the network.
Virues/trojan do exist that tries to steal your keys thats why hardware wallet are made :D