RE: Router / Protocol Problem
Good morning everyone. I just wanted to say thanks for all the help. I did discover the problem this morning and I should be hit with a herring. I upgraded the IOS on the router with the issue to match the other router and the problem was still there. So I tested and noticed the following line in the logs, since I was on console it popped up right in front of me. Sep 7 06:50:20.697 EST: %SEC-6-IPACCESSLOGP: list 166 denied tcp 69.50.222.8(25) -> 69.4.74.14(2421), 4 packets What is this I thought? What is my ACL 166 doing this? I thought I tested removing all access-lists from interfaces with the original problem came up. Apparently not. Here is my ACL 166, the first line is what was being matched. Apparently some how this connection is being matched via NBAR for good old Code Red. access-list 166 deny ip any any dscp 1 log access-list 166 deny tcp any any eq sunrpc access-list 166 deny tcp any any eq 135 access-list 166 deny tcp any any eq 137 access-list 166 deny tcp any any eq 138 access-list 166 deny tcp any any eq 139 access-list 166 deny tcp any any eq 445 access-list 166 deny tcp any any eq 5554 access-list 166 deny tcp any any eq 9996 access-list 166 deny tcp any any eq 1025 access-list 166 deny udp any any eq 1434 access-list 166 deny udp any any eq 135 access-list 166 deny udp any any eq netbios-ns access-list 166 deny udp any any eq netbios-dgm access-list 166 deny udp any any eq netbios-ss access-list 166 deny udp any any eq 445 access-list 166 deny icmp any any redirect access-list 166 deny ip 127.0.0.0 0.255.255.255 any access-list 166 deny ip 10.0.0.0 0.255.255.255 any access-list 166 deny ip 172.16.0.0 0.15.255.255 any access-list 166 deny ip 192.168.0.0 0.0.255.255 any access-list 166 permit ip any any class-map match-any http-hacks match protocol http url "*default.ida*" match protocol http url "*cmd.exe*" match protocol http url "*root.exe*" policy-map mark-inbound-http-hacks class http-hacks set ip dscp 1 I have always had this on my FE0/0 as an outbound ACL, well atleast since Code Red came about: ip access-group 166 out. Now I have two questions. Is that not a good idea to have this on FE0/0 out? Second, why the heck would a smtp connection be matched via my http-hacks class-map? Thanks again everyone, Mike -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Rodney Dunn Sent: Wednesday, September 06, 2006 8:45 PM To: Christopher L. Morrow Cc: Rodney Dunn; Mike Walter; Hank Nussbacher; Justin M. Streiner; nanog@merit.edu Subject: Re: Router / Protocol Problem Then that proves it's not a local router problem then. :) On Wed, Sep 06, 2006 at 07:49:26PM +0000, Christopher L. Morrow wrote:
On Wed, 6 Sep 2006, Rodney Dunn wrote:
Get a sniffer trace. Packets on the wire prove what's going on.
provided the packets get back to him, it seems his problem is traffic getting back to him :( so probably no packets will be on the wire (none in question atleast)...
On Thu, 7 Sep 2006 07:27:16 -0400 "Mike Walter" <mwalter@3z.net> wrote:
Sep 7 06:50:20.697 EST: %SEC-6-IPACCESSLOGP: list 166 denied tcp 69.50.222.8(25) -> 69.4.74.14(2421), 4 packets [...] I'm not very familiar with NBAR or how to use it for CodeRed, but this first rule:
access-list 166 deny ip any any dscp 1 log
Seems dubious. So I'm not not sure what sets the codepoint to 000001 by default, but apparently CodeRed does? Nevertheless, this seems like a very weak basis for determining whether something is malicious.
access-list 166 deny tcp any any eq 5554 access-list 166 deny tcp any any eq 9996 access-list 166 deny tcp any any eq 1025 access-list 166 deny udp any any eq 1434
You may realize this, but I bet some of the rules above I bet are matching on the occasional legitimate packets. Particular the last four rules above. In fact, I bet the rule that matches on TCP destination port 1025 probably has a lot of falsepositives. I'm not sure what you're trying to do with some of them, but if it is to stop some sort of worm, presumably you know that it will also stop applications that happen to choose those source ports. Windows hosts and apps will probably match the 1025 rule fairly frequently, UDP and NTP will match the UDP rule occasionally and various things will the others more or less frequently depending on what traverses your net.
Now I have two questions. Is that not a good idea to have this on FE0/0 out? Second, why the heck would a smtp connection be matched via my http-hacks class-map?
You don't show the interface config, but my guess is that the SMTP- looking packet may have originally had a codepoint of 1 and didn't really have anything to do with your policy-map. John
Hi John, John Kristoff wrote:
On Thu, 7 Sep 2006 07:27:16 -0400 "Mike Walter" <mwalter@3z.net> wrote:
Sep 7 06:50:20.697 EST: %SEC-6-IPACCESSLOGP: list 166 denied tcp 69.50.222.8(25) -> 69.4.74.14(2421), 4 packets [...] I'm not very familiar with NBAR or how to use it for CodeRed, but this first rule:
access-list 166 deny ip any any dscp 1 log
Seems dubious. So I'm not not sure what sets the codepoint to 000001 by default, but apparently CodeRed does? Nevertheless, this seems like a very weak basis for determining whether something is malicious.
It's his NBAR config lower down that sets the dscp value: class-map match-any http-hacks match protocol http url "*default.ida*" match protocol http url "*cmd.exe*" match protocol http url "*root.exe*" policy-map mark-inbound-http-hacks class http-hacks set ip dscp 1 So, there's probably two things that could happen here: One, NBAR is incorrectly identifying the SMTP traffic as code red, or two, the SMTP traffic is already marked with dscp 1. If you've using these values internally in your own network then they should be reset on all externally received traffic. Sam
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Seems dubious. So I'm not not sure what sets the codepoint to 000001 by default, but apparently CodeRed does? Nevertheless, this seems like a very weak basis for determining whether something is malicious.
There is an elegant solution; administrators should set the evil bit on any malicious packets seeking egress; http://www.faqs.org/rfcs/rfc3514.html Quoting: 0x0 If the bit is set to 0, the packet has no evil intent. Hosts, network elements, etc., SHOULD assume that the packet is harmless, and SHOULD NOT take any defensive measures. (We note that this part of the spec is already implemented by many common desktop operating systems.) 0x1 If the bit is set to 1, the packet has evil intent. Secure systems SHOULD try to defend themselves against such packets. Insecure systems MAY chose to crash, be penetrated, etc. And now for something completely different... - -- The whole point of the Internet is that different kinds of computers can interoperate. Every time you see a web site that only supports certain browsers or operating systems, they clearly don't get it. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.2 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFFAI/WPlSPhv5tocwRAnhrAJ40WgDRn+9fSPXa5U4qZGRRGRbjowCfbBxI AaDLCfYgGF1MjcieyDvuuME= =pibC -----END PGP SIGNATURE-----
participants (4)
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John Kristoff -
Mike Walter -
Sam Stickland -
Travis Hassloch