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Posted on 2004-05-03
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Last Modified: 2010-04-20
Hello experts,

I get a strange message on my linux box. It always pop au on my screen and it says:

172.31.217.5 sent an invalind ICMP error to a broadcast.

Can enybody tell my what it can means?

thanks

Luxana
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Question by:Luxana
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LVL 8

Expert Comment

by:da99rmd
ID: 10976168
Some one is sending an invalid ICMP packet to you, probobly someone infected with some virus or some trojan of some kind.
Do you know the computer with that ip ?

/Rob
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Expert Comment

by:da99rmd
ID: 10976175
Nothing to be alarmed on do you have a firewall up and running ?
ANd what service are appending the message ?

/Rob
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Author Comment

by:Luxana
ID: 10976325
this IP 172.31.217.5 is not on my network at all.

I'm blocking some ports with iptables and I'm traing to get my shorewall on.

I do not know which servise is appendig to this message . How can I found out?
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Expert Comment

by:da99rmd
ID: 10976403
I guess it appeard in /var/log/messages right ?
if so the [(service)] will tell you what service thats addes this entry.

/Rob
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by:Luxana
ID: 10976509
Rob

here is what I foud in /var/log/messages

May  2 10:52:00 luxana kernel: 172.31.217.5 sent an invalid ICMP error to a broadcast.
May  2 10:55:10 luxana kernel: 172.31.217.5 sent an invalid ICMP error to a broadcast.

it is also from another IP:

May  2 10:55:12 luxana kernel: 172.31.217.1 sent an invalid ICMP error to a broadcast.

what you thing?
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Accepted Solution

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da99rmd earned 80 total points
ID: 10976575
Ill just explain this
< --- date ------><--service->  <--------------- message ---------------------------------->
May  2 10:55:12 luxana kernel: 172.31.217.1 sent an invalid ICMP error to a broadcast.

So it was from the kernel the message arrived.

Then it was just so that an invalid ICMP packet arrived from that host 172.31.217.5 the reasons can be:
The host 172.31.217.5 was infected of som virus or trojan.
Or there where some korruption of the packet on the way to your computer.

Are there many entrys or just these ?

/Rob

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Author Comment

by:Luxana
ID: 10976625
there are many entres like this above. It starts

May  2 06:50:04 till now. I have no messages before it starts.

this is firstone:

May  2 06:47:04 luxana syslogd 1.4.1#10: restart.
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Author Comment

by:Luxana
ID: 10976650
Rob I have absolutely different netmask so I have no idea where this IP above is from..
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Author Comment

by:Luxana
ID: 10976651
Rob I have absolutely different netmask so I have no idea where this IP above is from..
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Expert Comment

by:da99rmd
ID: 10976655
Oki,
what ISP do you have ?
And are you on the 172.31.217.0 net ?

YOu can write the ISp and tell them that the host are sending strange packets, just to infomr them.

/Rob
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Expert Comment

by:da99rmd
ID: 10976671
Oki its some kind of broadcast you can just ignore it if its not bursting at your host.
Or just block it in your iptables rules.

/Rob
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Author Comment

by:Luxana
ID: 10976745
My isp is on totally different subnet so really I have no idea whre the meesage is from.

my intternal net is 192.168.0.0
ent extrernal have just 3 hosts


Rob just now I get my firewall working so it seems like I'm filly protected. So now I have to go and I'll check it tomorow and accept your answer.

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LVL 10

Author Comment

by:Luxana
ID: 10984760
rob  for help and patient no messages from yesterday when I start firewall.

thanks you

Luxana

http://www.experts-exchange.com/Operating_Systems/Linux/Q_20976691.html
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