I have a router and/or a firewall, is that it then ?Not quite. Remember, you need to employ a multi-layered security approach, and you need to address potential viruses/trojan horses/backdoors.
In addition to NAT and SPI firewall, you also need anti-virus and anti-trojan programs. After that, you must always keep current with virus-definition updates and OS/program security patches, always use strong passwords when sharing resources, and test your system for potential vulnerabilities using our online Security scan, or another portscan utility.