Snort mailing list archives
Re: Is this a valid traffic?
From: Joe Matusiewicz <joem () nist gov>
Date: Wed, 03 Apr 2002 14:02:02 -0500
At 12:39 PM 4/3/02, Skip Carter wrote:
-- the packet size is 1500 bytes. There is never any reason for an ICMP packet to be larger than 128 bytes.
I see these all the time and have commented this rule out. This looks like the MTU discovery that comes with some of the newer *nix versions. A ping packet is sent out with
a "don't fragment" bit set, 1500 bytes in size, and if a remote router can't forward the packet on a smaller MTU channel (say some old serial link), it will return a "can't fragment" ICMP pkt. to the web server, which will then lower the packet size for that host. In today's internet, those who can't handle a 1500 byte packet should be < .1%, so all that traffic is extraneous.One of our groups shut this off in their AIX web server a year ago because folks were complaining that they were getting ping scanned from it. They upgraded the OS on Monday and guess what -- it was turned back on by the upgrade. They shut it back off. I've also seen this behavior in Solaris and HP-UX.
-- Joe _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
Current thread:
- Is this a valid traffic? Onie Camara (Apr 03)
- Re: Is this a valid traffic? Skip Carter (Apr 03)
- Re: Is this a valid traffic? Joe Matusiewicz (Apr 03)
- Re: Is this a valid traffic? Chris Green (Apr 03)
- Re: Is this a valid traffic? Skip Carter (Apr 03)