MuleSoft Error Multiple "No listener found for request" for Non-Existence Paths

SYMPTOM

You can see that are multiple entries within the log files of requests being randomly trying URL paths, for example:

​No listener found for request:(GET)/admin/i18n/readme.txt

​No listener found for request:(GET)/a2billing/admin/Public/index.php

​No listener found for request:(GET)/current_config/passwd

​No listener found for request:(GET)/recordings/

​No listener found for request:(GET)/.git/objects

CAUSE

These HTTP requests would appear to be the result of something scanning the IP address that your application is running on. Once the IP address has been validated, it can be used in bot attacks that are attempting to exploit well-known URL's that are considered to be vulnerable for applications like WordPress or git repositories, for example.

SOLUTION 

This is a well-known issue for which there is really is no permanent solution. If your server has open Internet access then this sort of probing is not unusual.

An immediate solution would be to whitelist the IP's that you want to access this server. This will restrict he access to only known IP's and will introduce a potential administration overhead.

Another potential solution to this issue would be to change the IP address. This would just stop the tests until the IP of the application is identified again. 

It would be a wise precaution to review the URL patterns that are being used and see if there could be an issue of hitting something on your server. It's more of issue if you're seeing unexpected access to a server, rather than the listener not being found.