Security Incidents mailing list archives
Re: Strange kernel happenings
From: Ryan Russell <ryan () securityfocus com>
Date: Thu, 1 Nov 2001 10:54:53 -0700 (MST)
On Thu, 1 Nov 2001 mstevenson () quickhire com wrote:
< ksum from 63.94.31.225! < IP_MASQ:reverse ICMP: failed checksum from 63.94.31.225! < IP_MASQ:reverse ICMP: failed checksum from 141.198.38.114! < IP_MASQ:reverse ICMP: failed checksum from 63.94.31.225! < IP_MASQ:reverse ICMP: failed checksum from 63.94.31.225! < IP_MASQ:reverse ICMP: failed checksum from 63.94.31.225! < IP_MASQ:reverse ICMP: failed checksum from 65.205.2.1! the IP's however, are not consistent. Usually different IP's every day. I've tried to look this up, but am having a hard time finding information on what this means. Kinda looks like someone from the outside world is spoofing IP's, sending ICMP traffic to the server, but when the server tries to verify with a reverse lookup it flags and says "I don't like ICMP traffic from this address because it looks suspicious!" Any ideas anyone?
Every IP packet has a checksum attached to it, to help detemine if the packet has arrived intact. If the packet has been corrupted in some way, the cheksum will not match the rest of the packet. The normal reason for these to occur is a flakey network connection. Packets with a bad checksum will normally be dropped by any router, to this implies that it's the connection between your machine and its default gateway that is having trouble. It's theoretically possible that an attacker on the same layer 2 segment as you is purposely crafting invalid packet to some end, but of coure the bad network theory seems much more probable. Ryan ---------------------------------------------------------------------------- This list is provided by the SecurityFocus ARIS analyzer service. For more information on this free incident handling, management and tracking system please see: http://aris.securityfocus.com
Current thread:
- Strange kernel happenings mstevenson (Nov 01)
- Re: Strange kernel happenings Ryan Russell (Nov 01)
- <Possible follow-ups>
- RE: Strange kernel happenings NESTING, DAVID M (SBCSI) (Nov 01)
- RE: Strange kernel happenings Boyan Krosnov (Nov 01)