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Re: FTP denial of service attack
From: deraison () CVS NESSUS ORG (Renaud Deraison)
Date: Tue, 7 Dec 1999 18:46:05 +0100

On Tue, 7 Dec 1999, Darren Reed wrote:

Who has more free file descriptors & network ports, you or the ftp server ?

The attack you are describing is not new - this is just a PASV attack,
which has been around for years.

Hopefully, this problem is now solved.

Most modern FTP servers will :

        - either issue an error when they are issued a second
          PASV command

        - either accept the new PASV command, but they will close
          the previously open socket, so the FTP server has only
          two fd's open at a time.

If your FTP server server do not do this, use a real one.

                                -- Renaud

Renaud Deraison
The Nessus Project - http://www.nessus.org

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