TO OP. you need to do the following things in sequence
Download MBAR(MalwareBytes Anti RootKit Utility)
then whip on over to
Gibson research company and use the shields up utility to scan your ports for visibility to hackers.
https://www.grc.com/x/ne.dll?bh0bkyd2If you are afraid of this because of the dll file extension, search google about this company. They are the leading firewall research and development company in the world. Anyway, when you get there use the utility(which is quite ugly and a bit confusing) to scan all of your common service ports. green means they are in stealth and not visible. red means they are visible and open. blue means they aren't visible but your computer sent a response when the request was received, making the port vulnerable to various hack attempts. if all of your ports are in stealth mode then it is next to impossible for a hacker to find your computer unless they know your ip address.
After you have done all this research what ever coin clients you use's rpc port and default port and scan all of these manually.
Additonally, i would recommend downloading ccleaner from piriform, malware bytes pro, microsoft security essentials, avast internet security and sandboxie. i run all of these programs simultaneously with no problem and haven't had an infection in months, despite several attempts, including one by a forum member who coaxed me into a skype chat.
This is unnecessary. In general, you should never depend on
software to secure your system.
As long as the OP had no viruses on the offline computer before setting things up (do a clean OS install), disables autorun to protect from a USB transfer virus, and encrypts the offline computer with a strong password to guard against physical use he is perfectly safe (provided his paper backups remain so) because the private keys to spend coins are not accessible to the outside world, period. It doesn't matter if the online computer ever gets infected. No coins can move without being signed by the encrypted offline computer.