You should do a port test although most viruses end up on the PC due to a dodgy USB stick or a file accepted and so allowed though or simply bypass the Firewall.
Most Routers have a Firewall bulit in using NAT and with one click your protect yourself from many baddies straight off.
Oldie but goldie
https://www.grc.com/x/ne.dll?bh0bkyd2
Useful also
http://www.canyouseeme.org/
http://www.t1shopper.com/tools/port-scanner/
