I'm having two problems with smtp_backdoor.nasl plugin 18931, "SMTP server 
on a strange port".

First, the script name is defined incorrectly. It is given as: " 
script_name(english: 'SMTP server on a strange port');" which shows up 
correctly in nessus clients but totally confuses Lightning - resulting in 
a blank name and being unable to view any information about the plugin.

It should be defined as follows:

 name["english"] = "SMTP server on a strange port";
 script_name(english:name["english"]);

Second, we've got several FTP servers with restrictions to only allow 
selected hosts to connect. When nessus tries to connect 
(ftpserver_detect_type_nd_version.nasl plugin 10092), the banner is given 
as "530 Connection refused, unknown IP address." but it is correctly 
identified as an ftp server.

530 is a legitimate response for an FTP server as given in RFC-959, 
defined as "Not logged in." (combination of 5yz Permanent Negative 
Completion reply and x3z Authentication and accounting - Replies for the 
login process and accounting procedures.)

However, this is being detected as an SMTP server by 
find_service_3digits.nasl plugin 14773, " Identifies services like FTP, 
SMTP, NNTP...". This then causes 18931 to complain about a "backdoor set 
up by crackers to send spam" which makes some people unhappy.

Not sure what the best way to resolve this false positive is. 

Jerry Heidtke

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