and then use a hardware-wallet and be even more secure:
https://bitcointalksearch.org/topic/overview-bitcoin-hardware-wallets-secure-your-coins-899253

On my Linux which is running Ubuntu 14.10,I don't use anything. It's not needed on Linux at the moment and most likely will never be needed.
https://www.malwarebytes.org/
Most anti-virus programs are really not going to protect your bitcoin because most malware/virus are going to be custom made by people with the specific intent of stealing your specific bitcoin/private keys. Any antivirus program will likely not be able to catch such programs