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I have tested this in the past and the result always was that my PC is invisible, because it does not respond to ping and all ports are in stealth mode. However, when I ran the test today I found that it responds to ping and port 113 IDENT is closed instead of stealth.
Does anybody know how I can make this port invisible too and how I can make my computer clear not to respond to pings? Might there be updates (SuSE or KDE) that changed the security level?
In SuSE 9.3 you can edit /etc/sysconfig/SuSEfirewall2 to stealth port 113. I had the same report from ShieldsUP!, and editing the settings for this port and the policy for ping (Note: on a standalone PC) now give me 100% stealth result from Gibson's security test. There is lot of comment in SuSEfirewall2 to help you along.
You seem to allow icmp which ping uses, and reject port 113 instead of dropping or just plain not including it in the script. Like bibh_lnxq said, have a look at your firewall script. icmp is needed for some stuff though, like scp transfers with fish, so you might want to consider allowing it.
btw, not everyone feels shieldsup is a good test http://www.grcsucks.com/
The scan results are likely correct. SuSE intentionally leaves ident as CLOSED rather than stealthed for a reason. Certain services (like irc and some ftpd) require that queries to the clients ident port return at least some type of response before a connection is allowed. If SuSE left it closed then certain services would break for some users.