Being online is fraught with dangers: Internet worms, spyware agents, Trojan horses, hijackers and more can wreak havoc, causing anything from slow performance to system crashes to full-blown identity theft. And to provide you with the kind of protection you need in these days of cyberthieves and online extortionists, your firewall must be able to monitor all inbound and outbound traffic and protect you from any unauthorized intrusion by rendering your PC invisible to anything that you haven?t authorized to see it.