Re: Please help with this strangeness

[JGrimshaw () ASAP com]

Hi Michael,

I do not believe you have it quite right on the addressing description.

There would have to be four addresses--maybe a /30.  It is unlikely you 
were assigned just three addresses--at least, I have never seen it happen.

Perhaps your IP addressing is 81.174.224.68-71 /30?

You would then have the following:

.68 subnet address
.69 assignable
.70 assignable
.71 broadcast.

.72 could begin a new block of /30 addresses with .72 being the broadcast 
belonging to someone else.  (Hey, I am only guessing based on what you 
suggested).  Likewise, the block before you would start with 64 and end 
with 67.

It would seem that if .69 is sending out these pings, which you say is the 
router.

There would appear to be something else going on, so I am guessing you 
have private addresses internally and they are being NATed?  How is the 
router connected?  I do not understand how the IP address of the router is 
connecting to anything other than a point-to-point (if my /30 suggestion 
is true, which it probably is not) with another IP in the same range.  You 
have said the .70 is associated with another server that is not in use, so 
my guess is that the router is not connected to it.  So I am not sure what 
to think about that--can you provide more details?  Make up numbers if you 
like, or use x.x.x.x and depict subnets.

If the router has this .69 address, I would expect then that everyone is 
being NATed to use that address to access the internet?  Are you using NAT 
overload?
If this is the case, you may wish to sniff the internal segment and see 
where the ICMPs are coming from--having an IDS on the outside will not 
determine the  internal source IP address, just the NATed one.







Michael Thompson <mike () thompsonmike co uk> 
01/14/2004 09:03 PM
Please respond to
Michael Thompson <mike () thompsonmike co uk>


To

cc

Subject
Please help with this strangeness






Hi Security-basics,


I was going through all my security logs today and I noticed something
a little odd, and wonderd if anyone could offer any insight? I am not
that good at detailed security!

I have a IPBlock assigned from my ISP, where 81.174.224.68 to
81.174.224.70.

As I understand it, 68 is a broadcast address, 69 is assigned to the
router, 70 is for a server, which I dont use at the present time.

Now, in my snort logs, which is connected to the outside of the
firewall I get the following logs..

[**] [1:483:2] ICMP PING CyberKit 2.2 Windows [**]
[Classification: Misc activity] [Priority: 3] 
01/15-02:49:35.625784 81.174.224.69 -> 81.174.224.70
ICMP TTL:111 TOS:0xA0 ID:45600 IpLen:20 DgmLen:92
Type:8  Code:0  ID:512   Seq:52213  ECHO
[Xref => http://www.whitehats.com/info/IDS154]

[**] [1:483:2] ICMP PING CyberKit 2.2 Windows [**]
[Classification: Misc activity] [Priority: 3] 
01/15-02:49:35.641759 81.174.224.69 -> 81.174.224.68
ICMP TTL:110 TOS:0xA0 ID:45598 IpLen:20 DgmLen:92
Type:8  Code:0  ID:512   Seq:51701  ECHO
[Xref => http://www.whitehats.com/info/IDS154]

[**] [1:483:2] ICMP PING CyberKit 2.2 Windows [**]
[Classification: Misc activity] [Priority: 3] 
01/15-02:49:35.642071 81.174.224.69 -> 81.174.224.70
ICMP TTL:110 TOS:0xA0 ID:45600 IpLen:20 DgmLen:92
Type:8  Code:0  ID:512   Seq:52213  ECHO
[Xref => http://www.whitehats.com/info/IDS154]

[**] [1:483:2] ICMP PING CyberKit 2.2 Windows [**]
[Classification: Misc activity] [Priority: 3] 
01/15-02:49:35.649566 81.174.224.69 -> 81.174.224.71
ICMP TTL:111 TOS:0xA0 ID:45601 IpLen:20 DgmLen:92
Type:8  Code:0  ID:512   Seq:52469  ECHO
[Xref => http://www.whitehats.com/info/IDS154]

[**] [1:483:2] ICMP PING CyberKit 2.2 Windows [**]
[Classification: Misc activity] [Priority: 3] 
01/15-02:49:35.665945 81.174.224.69 -> 81.174.224.71
ICMP TTL:110 TOS:0xA0 ID:45601 IpLen:20 DgmLen:92
Type:8  Code:0  ID:512   Seq:52469  ECHO
[Xref => http://www.whitehats.com/info/IDS154] 


Now, I thought of welchia or one of its many variants, and all
machines are clean, the DHCP records show only one machine on the
network connected mostly, thats my machine. It's clean.

What could be causing these broadcasts? Any one have any ideas?

-- 

Best regards,
 Michael (mike () thompsonmike co uk)
 
Join the American Non-Sequitur Society -- we don't make sense, but we do 
like pizza. 

http://www.thompsonmike.co.uk/
PGP KeyID := 0xA9547E32

'To see a world in a grain of sand
And heaven in a wild flower
To hold infinity in the palm of your hand
And eternity in an hour'

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Running On Windows XP (2600, Service Pack 1)
Sent From OneAndOne

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