MSSQLSERVER event ID 18456 "Password did not match that for the login provided" filling log

(Windows 2012 R2 server with SQL 2012.) Windows Application log is filled with the following informational event several times a minute.

Login failed for user <user name>. Reason: Password did not match that for the login provided. [CLIENT: <IP>]

The user name is a SQL login name and not a Windows account. I believe this account is used by all users within the SQL application but I am not sure. The IP address shows those for many different computers from different subnets. The event is reported all hours of the day except maybe between midnight and 4:30 am.

Short of checking all the PC's and a large number of scheduled tasks on the SQL server, is there a simple way to determine where these are coming from?

Thank you.
realtimerAsked:
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Neil RussellTechnical Development LeadCommented:
Goto one of the computers with the IP address listed and do the following in a CMD prompt

C:\> NETSTAT -bn

now look for the IP Address of your SQL Server in the out, the executable connecting to the server will be listed on he line directly below.
arnoldCommented:
How are the sql credentials when a single set is used by all users is setup in the application?
If it is hardcoded meaning during the install it is set, than the question goes whether it ever worked on that system.
or whether it has recently changed when a new version was reinstalled but that system was skipped/missed.

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Vitor MontalvãoMSSQL Senior EngineerCommented:
realtimer, do you still need help with this question?
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