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Port 21
Link Logger for Windows
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Link Logger for Windows

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TCP Port 21

Common Use

FTP Service is typically is server where you upload/download files from.

Inbound Scan

If you are running a FTP server and have forwarded port 21 on your firewall then you need to setup a port forward within Link Logger such that future inbound traffic on this port will be logged as normal and not as an alert.

There are scans which look for FTP Servers, either anonymous or with weak passwording or have vulnerabilities.  Also some virus or trojans use FTP to download components.

Outbound Scan

By default Link Logger raises an alerts on outbound traffic to this port in order to alert administrators to use of unauthorized FTP servers.  Servers can be trusted such that future traffic to the authorized FTP server will not appear as an alert.

Additional Information

ProFTPD fails to properly handle newline characters when transferring files in ASCII mode

WS_FTP Server vulnerable to buffer overflow when supplied overly long "APPE" command

WS_FTP Server vulnerable to buffer overflow when supplied overly long "STAT" command

Page last updated on February 09, 2004