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Does Fetch automatically do a "port scan"? (4 posts)

  • Started 11 years ago by Karen
  • Latest reply 11 years ago from Karen
  • Karen Member

    One of our programmers was using Fetch to upload files from her Mac to our Mac server. In the middle of the upload, our virus checking software (Intego Virus Barrier) cancelled the upload because it caught a "port scan" (sign of a potential hacker). She had been uploading files before this without problem. No one else was on the server.

    Does Fetch automatically do anything like a "port scan" when it's uploading a directory?


    Posted 11 years ago #

  • Jim Matthews Administrator

    The short answer is that no, Fetch does not scan ports, but that the nature of the FTP protocol is such that uploading lots of files in a short period could be mistaken for a port scan.

    The normal way that FTP works involves having the client (Fetch) open a connection to the server for each file being uploaded. The server picks which TCP port the client will connect to, picking a different port for each transfer, and often picking them in sequence (e.g. ports 49623, 49624, 49625, …). From the point of view of Intego Virus Barrier that may look like a systematic effort by a hacker to look for open ports.

    I would ask Intego to see if they have a way to turn off port scan detection. Alternatively, you could see whether the programmer could use SFTP rather than FTP; it's more secure, and does not involve creating a new connection on a new port for every transfer. Finally, if none of that works, the programmer could uncheck "Use passive mode transfers (PASV)" in the General section of Fetch preferences. That reverses the direction of the FTP data connections, so the server connects back to Fetch, and therefore should avoid this issue.


    Jim Matthews
    Fetch Softworks

    Posted 11 years ago #

  • Karen Member


    Thanks for the explanation! I did write Intego about this. They told me how to restore the user's connection. I waiting to hear about how to prevent this in the future.

    We'll try your suggestions!


    Posted 11 years ago #

  • Karen Member


    It worked! She unchecked "Use passive mode transfers (PASV)" in Fetch, and she uploaded another directory. No problem with Virus Barrier!


    Posted 11 years ago #


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