Quick, subjective, gut-response analysis: YMMV. :-) I'd do some closer looking at the source machine. I'm somewhat wary of trusting the user to just run a AV scan. This may be a new piece of malware that doesn't have an AV def. yet. Or the user may be doing something wrong. Apply the standard IR procedures. Especially use netstat -an for open connections and fport to map processes bound to individual ports. Based on the destination, I'm guessing that 10.1.2.3 is compromised and being used as a bot to perform a DoS (maybe distributed) against an IRC server run by AOL. Are the MS networking ports (135-139, 445) exposed to the Internet? Does the Admin account have a weak/null password? The sig is firing b/c protocol 255 is reserved and you shouldn't see packets w/ that protocol type (http://www.iana.org/assignments/protocol-numbers). I'm guessing this is being used either to evade detection by some weaker forms of IDS or to slip through packet filtering devices that are only inspecting TCP, UDP, ICMP, etc. Do you have an idea of the volume of packets that were coming from this source? What was the rate in pps? Are you running Cisco Netflow? If so, check those logs. Please let me know if you have any questions. Thanks! Jason Falciola Information Security Analyst IBM Managed Security Services falciolaat_private DY <dybulkat_private> 03/13/2003 04:53 PM To: incidentsat_private cc: Subject: unidentified DOS "bad traffic" Hi all, I'm quite surprised at the lack of material I'm turning up in researching this issue, so I'm resorting to this post. Please feel free to point me somewhere. Twice in the past week I have experienced a severe DOS condition on my network. A particular host has been completely flooding the network with some sort of traffic that chokes the whole thing. Now, on the first incident I was unable to obtain packet trace data (I'll spare the details) and was forced to reconnect the particular segment's port. We got by for a few days, and then wham, it happened again. This time I isolated the segment with a Snort sensor and captured a large amount of data (actually, I only sniffed for a few seconds before I'd already swallowed about 10 MB of data, all of which was identical, so I stopped). My Snort output on this trace was filled with nothing but bizillions of these entries (payload did vary a little): 03/13-07:53:50.650383 10.1.2.3 -> 64.12.165.57 PROTO255 TTL:128 TOS:0x0 ID:50456 IpLen:20 DgmLen:80 45 10 00 3C B5 F5 40 00 40 06 E8 85 CD A2 E9 48 E..<..@.@......H 40 0C A5 39 D3 A6 1A 0B BC C0 DE 3C 00 00 00 00 @..9.......<.... A0 02 7D 78 D3 8E 00 00 02 04 05 B4 04 02 08 0A ..}x............ 00 CD 7F 52 52 00 00 00 01 03 03 00 ...RR....... =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ The source IP is from a private network that I run, which uses basic NAT, so I can certainly route and identify the host, as this capture is from the private side of the NAT router. Now, here's the Snort alert entry (again, just thousands of this same entry): [**] [1:1627:1] BAD TRAFFIC Unassigned/Reserved IP protocol [**] [Classification: Detection of a non-standard protocol or event] [Priority: 2] 03/13-07:53:11.032136 10.1.2.3 -> 64.12.165.57 PROTO255 TTL:128 TOS:0x0 ID:23977 IpLen:20 DgmLen:80 Now, I've read up on the Snort signature that generates this alert (SID 1627). It says that it's bad traffic (of course) using an unassigned protocol, which of course the alert states. However, I'm not finding anything (Google, Usenet, etc.) that leads me toward the proper analysis of what this machine was doing. All I know is: 1) The machine runs Win2K pro. 2) The user has no idea what's going on, of course, and has scanned his machine with the latest AV updates, with no viri found. 3) IP address 64.12.165.57, the destination for this complete flood of "bad traffic," resolves (reverse) to irc-m.icq.aol.com. 4) There was so much of this traffic that it shut my network down. My main router (Cisco) reported no appreciable CPU consumption during the attack. It just appears that the sheer volume of the [bad] packets choked everybody out. So, I know of no exploit, no virus, no known malicious destination (which might lead me to an exploit)...and yet I had no throughput (except for the "bad traffic"). Can anybody give me a clue, or at least point me somewhere (probably obvious) that I seem to be missing? I might post to the Snort-users list as well, I guess, in case anybody there has ideas. Many TIA, -- DY ---------------------------------------------------------------------------- <Pre>Lose another weekend managing your IDS? Take back your personal time. 15-day free trial of StillSecure Border Guard.</Pre> <A href="http://www.securityfocus.com/stillsecure"> http://www.securityfocus.com/stillsecure </A>
This archive was generated by hypermail 2b30 : Fri Mar 14 2003 - 09:55:17 PST