Hi, Can I know on which machine you are running the tcpdump? Regards, Dharmendra T. nSecure Software On Sun, 2004-02-22 at 19:00, crv2 wrote: > hi, > > Does someone else observe the problem with Blaster spoofed flood attack > affecting Dhcpd daemon? > > The output from the Tcpdump -i eth1 -ne host 127.0.0.1 (eth1 - internal > interface): > 18:18:48.933129 0:a:cd:1:b:39 0:10:15:34:23:34 0800 60: 127.0.0.1.80 > > 10.0.143.221.1806: R 0:0(0) ack 357826561 win 0 > 18:18:48.943879 0:2:44:57:364 0:10:15:34:23:34 0800 60: 127.0.0.1.80 > > 10.0.192.42.1689: R 0:0(0) ack 83165185 win 0 > 18:18:48.955866 0:a:cd:0:a7:7f 0:10:15:34:23:34 0800 60: 127.0.0.1.80 > > 10.0.57.67.1197: R 0:0(0) ack 1552613377 win 0 > 18:18:48.956093 0:30:4f:20:e0:8b 0:10:15:34:23:34 0800 60: 127.0.0.1.80 > > 10.0.56.108.1893: R 0:0(0) ack 952369153 win 0 > 18:18:48.956519 0:30:4f:26:c7:96 0:10:15:34:23:34 0800 60: 127.0.0.1.80 > > 10.0.2.37.1812: R 0:0(0) ack 1434583041 win 0 > 18:18:48.956715 0:a:cd:1:b:39 0:10:15:34:23:34 0800 60: 127.0.0.1.80 > > 10.0.209.93.1642: R 0:0(0) ack 992411649 win 0 > 18:18:48.963920 0:2:44:57:364 0:10:15:34:23:34 0800 60: 127.0.0.1.80 > > 10.0.2.169.1524: R 0:0(0) ack 717750273 win 0 > > 00:10:15:34:23:34 out server DHCPd mac address > flood is about 1200p/s and from 4 different MAC's > > and another output (out client DHCP request with no response from out > server) > tcpdump -i eth1 -n udp port 67: > > tcpdump: listening on eth1 > 18:38:34.071188 0.0.0.0.68 > 255.255.255.255.67: xid:0x1e429414 secs:55030 > file ""[|bootp] > 18:38:35.702552 0.0.0.0.68 > 255.255.255.255.67: xid:0x1c6f144e secs:56566 > flags:0x8000 file ""[|bootp] > 18:38:36.298190 0.0.0.0.68 > 255.255.255.255.67: xid:0x4a34ea34 secs:57846 > flags:0x8000 file ""[|bootp] > 18:38:37.894439 0.0.0.0.68 > 255.255.255.255.67: xid:0xa41add0d secs:57846 > flags:0x8000 file ""[|bootp] > 18:38:40.527775 0.0.0.0.68 > 255.255.255.255.67: xid:0xb20b790e secs:59382 > flags:0x8000 file ""[|bootp] > > It seems that it is affecting only dhcpd daemon, on different version of > kernel and iptables. > iptables v1.2.9 and iptables v1.2.8 > kernel 2.4.23 and 2.4.24 > Internet Software Consortium DHCP Server V3.0pl2 > > And why iptables -I FORWARD -s 127.0.0.1 -i eth1 -j DROP and iptables -I > INPUT -s 127.0.0.1 -i eth1 -j DROP > does not blocking the traffic? > > Only solution is: iptables -I PREROUTING -t mangle -s 127.0.0.1 -i eth1 -j > DROP > After that Dhcpd starts working normaly again (And we are not 100% surre of > that) > > ifconfig lo down or ifconfig lo 192.168.1.1/32 does not work > > Any idea? > > > -- Dharmendra T. Linux Security and Admin, www.nsecure.net This message is intended for the addressee only. It may contain privileged or confidential information. If you have received this message in error, please notify the sender and destroy the message immediately. Unauthorised use or reproduction of this message is strictly prohibited.
