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File (FTP) blocking

FTP blocking

For security reasons the Computing Service blocks general access from outside the CUDN to FTP servers within. Specifically, connections from JANET into the CUDN to port 21 are blocked, except for a list of permitted CUDN hosts. This therefore affects users who need to provide an FTP server or similar facilities for use from outside Cambridge.

FTP initiated by an FTP client running within Cambridge is not blocked, wherever the server may be.  The list of exceptions to the block for non-CUDN calls includes the Managed Cluster Service (MCS) and Hermes.

The primary way round the block is to use an SSH server instead wherever possible, Users wishing to connect to the server then need to use an SFTP/SCP client, as described elsewhere (see lefthand menu).

Other alternatives are:

  • use the VPDN service to avoid the problem
  • arrange to initiate transfers using an FTP client within Cambridge (the block does not affect outgoing FTP).
  • use an intermediate machine not subject to the block as a staging post.
  • arrange that the relevant Cambridge system is adequately managed, both now and for the future, and apply through the appropriate institutional Computer Officer to to have it included in the exceptions list.
  • put the files on a Web server so that they can be accessed using HTTP.
  • small files (e.g. plain text or Word documents of a few pages) can readily be sent by e-mail, or even on memory sticks, CDs, ZIP disks etc .

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