Full Disclosure mailing list archives
Re: DHCP Flood on inside network. HELP!!
From: Gregory Gilliss <ggilliss () netpublishing com>
Date: Mon, 11 Oct 2004 23:53:18 -0700
Sounds like someone discovered the DHCP discover flood trick and set it to work on you. A little packet filtering kung fu on your part ought to be sufficient to prevent it happening again. -- Greg On or about 2004.10.11 22:00:07 +0000, Eddie (EddieS () softhome net) said:
I don't have much information on this yet, I am driving down to the office now to pull an all nighter. I figured I would toss this out to the list and see if anyone has any idea. This is just info from what I can get from talking to people and what little time I can get on the network before it goes down. Starting 2 days ago, I discovered the PIX 515 was locked hard. It seems to be random, but around every 15-30 minutes something floods the network hard for a few minutes. Broadcast flood too. This is a small network with 30 workstations and 5 servers (Linux and SCO, no Wins). It overloads the Extreme switches and I see pdu (or something like that, not udp tho) errors on about every port. The Pix 515 overloads and is having issues, but I did see it say something about ARP problems when I could get to the syslog for more info. I looked up the error number and it said it could be ARP poisoning. Not sure what would do that. In the syslog of the DHCP server, I see thousands of DHCP DISCOVER request(and the REPLAY request from the server, a Linux box). It looks like one client on the network (I have seen this both from XP and Win98) will send 100+ DISCOVER request a second swamping the network. Not always DISCOVER too. That will go on for a few minutes, then all is well. Then another computer will do the same thing. This is quickly overloading things and I am getting IRQ busy and overload errors on some of the servers. What should I look for. I have never seen something like this before. Thanks -Eddie _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
-- Gregory A. Gilliss, CISSP E-mail: greg () gilliss com Computer Security WWW: http://www.gilliss.com/greg/ PGP Key fingerprint 2F 0B 70 AE 5F 8E 71 7A 2D 86 52 BA B7 83 D9 B4 14 0E 8C A3 _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
Current thread:
- DHCP Flood on inside network. HELP!! Eddie (Oct 11)
- Re: DHCP Flood on inside network. HELP!! J.A. Terranson (Oct 11)
- Re: DHCP Flood on inside network. HELP!! Gregory Gilliss (Oct 12)
- Re: DHCP Flood on inside network. STP the problem? Eddie (Oct 12)