Windows 2003 Server Running Plesk now experiencing passive FTP issues 425 can't open data connection

FTP users are now getting 425 errors when using passive FTP (active seems to be working fine). These errors started occurring recently. We did make one firewall change recently to explicitly block UDP request on port 0, but that shouldn't have caused this (I even disabled that rule and tested to be certain it wasn't the problem).

Perhaps one of the recent Windows Updates changed something that caused passive FTP to stop working?
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CaltorConnect With a Mentor Commented:
To allow passive FTP your firewall will have to allow TCP connections on the random ports > 1023 used by your FTP server. You can check this with TELNET or FTP. I don't expect your UDP rule is causing the problem but it could have been the catalyst for applying a previously defined configuration that is now causing the issue.

What FTP server are you using? What firewall are you using?
See for guidance on troublshooting FTP Error 425.
ixoyefreakAuthor Commented:
You're right in that the firewall change was the catalyst. As it turns out it disabled an ALG for FTP. I re-enabled the application layer gateway and viola all is well again.

Well done. Glad to hear you got it sorted. I've been there before where you make a change and it's the catalyst for something sinister lurking, especially with unapplied changes to firewall rules. For future reference I forgot to mention there is a Microsoft article on troublshooting FTP error 425 at
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