Date: Fri, 14 May 1999 14:07:26 -0600 From: Brett Glass <brett@lariat.org> To: Don Lewis <Don.Lewis@tsc.tdk.com>, Thamer Al-Herbish <shadows@whitefang.com>, security@FreeBSD.ORG Subject: Re: Forwarded from BUGTRAQ: SYN floods against FreeBSD Message-ID: <4.2.0.37.19990514140618.046502a0@localhost> In-Reply-To: <199905140546.WAA06542@salsa.gv.tsc.tdk.com> References: <Thamer Al-Herbish <shadows@whitefang.com>
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At 10:46 PM 5/13/99 -0700, Don Lewis wrote: >One potential danger is that you can't totally block incoming connections >to vulnerable ports by filtering out incoming SYN packets. If an attacker >can guess what sequence number you would have sent in a SYN-ACK, he can >establish a connection by just sending the third packet in the initial >three-way handshake. This isn't especially easy to brute force because >the sequence space is a 32 bit number, but it's not totally unreasonable >either if the attacker is patient enough. The attacker may also be able >to make better guesses if he knows the details of the implementation he is >attacking. It can be made pretty tough to guess if one has a good entropy pool. --Brett To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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