HI

I'm new to knoppix/linux. Using Windows, I always ran Zonealarm firewall. With Knoppix, I feel "exposed" because there is no firewall. On the GRC Shields Up page It says I fail the Stealth test, but all ports show up as closed. Zone Alarm with Windows shows totally stealth.

I have 3 questions-

1-Is linux secure enough to use without a firewall?

2-Can I install a firewall (or other software) when running knoppix live from cd?

3-I understand the obvious security of not writing to the hard drive-only to the ramdisk, which disappears after rebooting. I've even run knoppix successfully with hard drive physically disconnected-so no chance of reading from it either. But does anyone know what kind of things hackers could do through your computer during a session-or is knoppix/linux not vulnerable like windows?