Re: Port 80 SYN flood-like behavior

[John Elliott <johne () trifidtech ca>]

On February 13, 2002 22:58 pm, Dave Dittrich wrote:
[snip]
> This attack used a variation of a TCP based reflection attack that is
> not widely known to exist in the wild.  Steve's early analysis of the
> attack in included below (Appendix A).
>
> While there may be a new (D)DoS program "in the wild" to implement this
> attack, the risks and methods have been known for two or more years
> and some simple modifications to existing tools, and a good list of
> high-capacity routers, switches, and servers, could affect an attack
> of this type.

I have two web servers on different networks that have been receiving this 
type of traffic for the last 2 or 3 weeks.  The same source IP's hit both 
hosts at about the same time.  This is low rate traffic and generates  ACK's 
back to the target.  I have been logging this activity for about two weeks 
and have captured some of the packets.  I suspect that more than one machine 
have the same reflector host list based on the varying times of day when 
activity occurs.

A partial solution is for network operators (more likely ISP's) to do egress 
filtering to ensure that only IP source addresses that belong to their 
network  leave their network.  

John Elliott

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