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ip spoof

Posted on 2014-11-26
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Last Modified: 2014-12-02
I just started to see these in our logs

Source       Destination                                  Cisco Event        Result
0.14.2.10    X.X.X.X one of our public IP's 106016             Deny IP spoof

There have been 10 in the last few mins but different source IP's starting with 0.

Excuse my ignorance but what does it mean when the IP address starts from 0.?

Many Thanks!
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Question by:Farmerbob212
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by:Dave Baldwin
Dave Baldwin earned 250 total points
ID: 40468122
0.x.x.x is a reserved block that is not available for public use.  http://www.iana.org/assignments/ipv4-address-space/ipv4-address-space.xml  It belongs to the Internet Assigned Numbers Authority (IANA).
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by:Farmerbob212
ID: 40469097
So if it is a private IP is it coming from within the network? I usually see (inside-network) 192.168.x.x
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Expert Comment

by:Dave Baldwin
ID: 40469510
Yes but 0.14.2.10 is not a 'private IP'.  It is in a reserved block for the Internet Assigned Numbers Authority (IANA) and you should never see it.   I don't know how they are managing to spoof that IP address.  I think it takes some low level programming to do that.
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Rich Rumble earned 250 total points
ID: 40472468
You can spoof the src with a variety of programs, nmap being one of he easiest, it's already built-in. Spoofing isn't very effective outside of UDP. You should have bogons being denied, that's all of RFC 1918 (10.x.x.x, 192.168.x.x, 172.16.x.x) as well as others you don't want:
http://www.cisco.com/web/about/security/intelligence/firewall-best-practices.html#_Toc332806011
https://supportforums.cisco.com/document/12013356/implementing-anti-spoofing-access-list
It's typically nothing to worry about, especially in the TCP protocol.
-rich
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Author Closing Comment

by:Farmerbob212
ID: 40476237
thank you very much for the advice!
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