i recently found a malware that changes bitcoin addresses when copied to the hackers address so just watch out and check to make sure that the bitcoin address you copy comes out the same when you paste it 
it is safer to store your coins on a hardware wallet:
https://bitcointalk.org/index.php?topic=899253.0
it is, but sometimes you need to pay for something online, you need to copy the addresses, it might be easier to check and find the flaw, but it is still a risk that the address sending too is changed when copy-pasted.
Thanks for the warning, do scan my devices regularly, not just for the bitcoin, better safe than sorry.