Security Incidents mailing list archives
Re: Port 80 SYN flood-like behavior
From: Stuart Sheldon <stu () actusa net>
Date: Wed, 13 Feb 2002 15:54:17 -0800
Yes, we are seeing the same thing over here... It appears to be most effective when the attack is pointed at a subnet with a shared web server with many IP's bound to the same interface. This also could be an attempt to use these system's as a reflector to flood a particular IP address out on the web... Stu Sheldon "NESTING, DAVID M (SBCSI)" wrote:
In the last few days I've been seeing what *looks* like a SYN flood attack on port 80 across all IP addresses on my network. However, if it's a flood, it's not a very strong one. Modest hardware is able to keep up with the incoming packets without a problem, but the steady flow of SYN packets is still a steady flow. (On a given system, the number of connections in a SYN_RECVD-ish state numbers 50-100.) The source IP addresses stay constant for a minute or two and then cease, sometimes as another IP address starts sending its own stream of SYN packets, though occasionally more than one host will be sending traffic at a time. Source addresses are in a variety of networks, but seem to be consistently dialup or similar type connections. It "feels" like an attempt at a denial-of-service attack, but why spread it out over so many destination IP addresses (many of which have no Internet presence), and why would the flood be so weak as not to actually affect anything? Could this be an IDS allowing spoofed IP addresses through while stripping out a "dangerous" payload that might come along with the first ACK response? Or maybe a form of scan where the volume of response carries information they want? Has anyone seen something similar? David ---------------------------------------------------------------------------- This list is provided by the SecurityFocus ARIS analyzer service. For more information on this free incident handling, management and tracking system please see: http://aris.securityfocus.com
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Current thread:
- Port 80 SYN flood-like behavior NESTING, DAVID M (SBCSI) (Feb 13)
- Re: Port 80 SYN flood-like behavior Stuart Sheldon (Feb 13)
- Re: Port 80 SYN flood-like behavior Matthew Leeds (Feb 13)
- Re: Port 80 SYN flood-like behavior Steve Gibson (Feb 13)
- Re: Port 80 SYN flood-like behavior Dave Dittrich (Feb 13)
- Re: Port 80 SYN flood-like behavior John Elliott (Feb 14)
- Re: Port 80 SYN flood-like behavior Dave (Feb 16)
- Re: Port 80 SYN flood-like behavior Dave Dittrich (Feb 13)
- Re: Port 80 SYN flood-like behavior Stuart Sheldon (Feb 13)
- Re: Port 80 SYN flood-like behavior Lewie Wolfgang (Feb 13)
- <Possible follow-ups>
- Re: Port 80 SYN flood-like behavior Thierry Zoller (Feb 14)
- Re: Port 80 SYN flood-like behavior Dave Dittrich (Feb 14)
- Message not available
- Re: Port 80 SYN flood-like behavior Steve Gibson (Feb 15)