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12-23-2005, 04:05 PM
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#1
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Member
Registered: Aug 2005
Distribution: SuSE Linux / Scientific Linux / [K|X]ubuntu
Posts: 273
Rep: 
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Port Scan: Closed Port instead of Stealth
Hi there!
On this website I have tested my internet vulnerability:
https://www.grc.com/x/ne.dll?bh0bkyd2
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?
I have my firewall up and running...
Thanks and happy holidays! |
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12-24-2005, 08:20 AM
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#2
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Member
Registered: Sep 2002
Posts: 310
Rep: 
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Can you post either your iptables script, or the output of iptables -L -n -v?
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12-24-2005, 08:41 AM
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#3
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LQ Guru
Registered: May 2005
Location: Atlanta Georgia USA
Distribution: Redhat (RHEL), CentOS, Fedora, CoreOS, Debian, FreeBSD, HP-UX, Solaris, SCO
Posts: 7,831
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Nice quote but unfortunately not quite accurate. Berkley did do a lot of development for UNIX after AT&T gave it to universities but it came out of AT&T Bell Labs originally.  |
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12-24-2005, 08:44 AM
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#4
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Member
Registered: Sep 2002
Posts: 310
Rep:
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This is my care face 
This is my not-care face
This thread is not about the history of Unix and LSD |
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12-24-2005, 08:59 AM
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#5
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Member
Registered: Nov 2004
Location: Leiden, Netherlands
Distribution: SuSE; Fedora;Slackware
Posts: 58
Rep:
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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.
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12-24-2005, 02:08 PM
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#6
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Member
Registered: Aug 2005
Distribution: SuSE Linux / Scientific Linux / [K|X]ubuntu
Posts: 273
Original Poster
Rep:
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Chain INPUT (policy DROP 1 packets, 73 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
388 236K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
state RELATED,ESTABLISHED
11 982 input_ext all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 1 packets, 73 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * lo 0.0.0.0/0 0.0.0.0/0
425 49966 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
state NEW,RELATED,ESTABLISHED
0 0 LOG all -- * * 0.0.0.0/0 0.0.0.0/0
limit: avg 3/min burst 5 LOG flags 6 level 4 prefix `SFW2-OUT-ERROR '
Chain forward_ext (0 references)
pkts bytes target prot opt in out source destination
Chain input_ext (1 references)
pkts bytes target prot opt in out source destination
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
PKTTYPE = broadcast
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
icmp type 4
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
icmp type 8
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
state RELATED,ESTABLISHED icmp type 0
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
state RELATED,ESTABLISHED icmp type 3
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
state RELATED,ESTABLISHED icmp type 11
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
state RELATED,ESTABLISHED icmp type 12
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 14
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 18
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 3 code 2
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 5
0 0 reject_func tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:113 state NEW
11 982 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain reject_func (1 references)
pkts bytes target prot opt in out source destination
0 0 REJECT tcp -- * * 0.0.0.0/0 0.0.0.0/0 reject-with tcp-reset
0 0 REJECT udp -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-proto-unreachable
linux:/home/pcbase # iptables -L -n -v
Chain INPUT (policy DROP 1 packets, 73 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
388 236K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
12 1046 input_ext all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 1 packets, 73 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * lo 0.0.0.0/0 0.0.0.0/0
425 49966 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state NEW,RELATED,ESTABLISHED
0 0 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 3/min burst 5 LOG flags 6 level 4 prefix `SFW2-OUT-ERROR '
Chain forward_ext (0 references)
pkts bytes target prot opt in out source destination
Chain input_ext (1 references)
pkts bytes target prot opt in out source destination
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0 PKTTYPE = broadcast
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmp type 4
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmp type 8
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 0
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 3
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 11
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 12
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 14
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 18
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 3 code 2
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED icmp type 5
0 0 reject_func tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:113 state NEW
12 1046 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain reject_func (1 references)
pkts bytes target prot opt in out source destination
0 0 REJECT tcp -- * * 0.0.0.0/0 0.0.0.0/0 reject-with tcp-reset
0 0 REJECT udp -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-proto-unreachable
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12-24-2005, 05:01 PM
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#7
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Senior Member
Registered: Dec 2004
Location: Helsinki
Distribution: Debian Sid
Posts: 1,107
Rep:
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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/ |
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12-24-2005, 05:22 PM
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#8
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Senior Member
Registered: Nov 2002
Location: Silly Con Valley
Distribution: Red Hat 7.3, Red Hat 9.0
Posts: 2,054
Rep:
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12-26-2005, 11:41 AM
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#9
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Member
Registered: Aug 2005
Distribution: SuSE Linux / Scientific Linux / [K|X]ubuntu
Posts: 273
Original Poster
Rep:
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I got the same result plus one closed other port from sygate: port 80 WEB and port 113 IDENT.
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12-26-2005, 08:51 PM
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#10
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Senior Member
Registered: Mar 2003
Distribution: Fedora
Posts: 3,658
Rep:
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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.
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