Snort mailing list archives
RE: ISD171/ping zeros - One legit use
From: "Ofir Arkin" <ofir () sys-security com>
Date: Fri, 1 Jun 2001 15:27:50 -0700
Rich, I can belive this is the case with DNS servers running HPUX 11.x, 10.3 or AIX 4.3.x. If so, the admin who set up the DNS server did not fully understand this issues obviously. With load balancing I am more skeptic. They balance the load on the Servers on site not on the coming clients... If you will download version 2.5 of my paper and go to page 45 you will have a full explanation. Cheers Ofir Arkin [ofir () sys-security com] Founder The Sys-Security Group http://www.sys-security.com PGP CC2C BE53 12C6 C9F2 87B1 B8C6 0DFA CF2D D360 43FA -----Original Message----- From: Rich Adamson [mailto:radamson () routers com] Sent: Friday, June 01, 2001 6:03 AM To: Ofir Arkin; Snort Users Postings Subject: RE: [Snort-users] ISD171/ping zeros - One legit use Ofir, I did search multiple web sites (including yours) and found nothing that suggests 1500 byte icmp requests have been observed in DNS/Load Balancing systems. Icmp's have been used for a lot of unusual things, however only one web site found any reference whatsoever to "IDS171" and that one did not even provide a hint relative to the response below. The original posting was intended to "add to" the list of what some might consider legitimate icmp uses. Rich ------------------------
This is an issue dealt in this mailing lists again and again :) You might wish to search the archives and find out that HPUX 11.x, 10.30, AIX 4.3.x has a 'unique' PMTU discovery process using ICMP Echo requests that produce the same patterns you described. You can also read the appropriate section in my paper ICMP Usage in
Scanning
available from http://www.sys-security.com. -----Original Message----- FYI... One of our sites has been observing: 09:49:15 snort[2907]: IDS171/ping zeros: x.x.x.x -> y.y.y.y from snort. The content of these ping packets is essentially 1500 bytes of zeros (0's), and were arriving from five IP addresses assigned around the world. In researching the "source" of these packets, we received the following response from this well-known international company: "What you are seeing is a Wide area load balancing system trying to figure out which of our 3 data centers is closest to you. Someone on your
network
requested one of our websites, and our DNS/load balancing system tries probing your nameserver that the initial dns request came from, and instructs the other data centers to do the same to collect path metrics. Subsequent requests from your network result in being handed an IP for the closest/fastest data center. http://www.f5.com has the relavent
information
on how the system works. If you'd like to be put in an exclude list, we can stop the probes to your network. It tries to be as quiet as possible, but is in no way malicious. It does tend to set off some IDS systems though."
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Current thread:
- ISD171/ping zeros - One legit use Rich Adamson (May 31)
- RE: ISD171/ping zeros - One legit use Ofir Arkin (May 31)
- RE: ISD171/ping zeros - One legit use Rich Adamson (Jun 01)
- RE: ISD171/ping zeros - One legit use Ofir Arkin (Jun 01)
- RE: ISD171/ping zeros - One legit use Rich Adamson (Jun 01)
- Re: ISD171/ping zeros - One legit use Sid (May 31)
- RE: ISD171/ping zeros - One legit use Ofir Arkin (May 31)