The firewall's there to prevent something like a malicious scanning app or routine from connecting to the system. Generally a virus gets past your firewall & on your system because you allowed it, whether by receiving a malicious email, downloading something because you visited a malicious web site, and so on. Viruses do not really sneak around firewalls - I think maybe you misunderstand how they work & what they're for. A web page or ad on a web page can contain malicious javascript or Flash, though if you install all patches & updates, use an ad blocker, & stick to known good sites, like GOTD, you'll most probably be OK.

One of the oldest is to offer malware infected files for download, drivers or otherwise.

There are all sorts of ways, exploits to compromise a PC or server. Most viruses sneak behind the firewalls or when clicking on links or when downloading software.' viruses are hidden in the drivers you update. Most however is designed to make a cybercriminal money, &/or to steal data - in both cases the party responsible wants it to survive a long time undetected, so it will store something on the device to make sure it sticks around. Some malware does have a destructive purpose, like deleting files, & then there's no purpose for it hanging around. 'Most viruses act in real time mode and are not stored inside your computer.' How it manages that 2nd part varies by brand as well as the package you've bought, as more expensive products within the same brand offer more protection to justify their higher price. It'll also monitor what's going on when you're using Windows, & hopefully stop anything that appears like it might be up to no good. A good security suite will use a database of known malware signatures, and if it detects code in a file that matches one of those signatures it'll block it, usually by quarantining it. Actually the best way to read about what security software does is to visit the web site for whatever brand you're interested in.

Malware hunter pro 1.57code