Extended Events - list servers connecting to your SQL Server.

gistfile1.sql

-- If the Event Session Exists, drop it first
IF EXISTS (SELECT 1 
			FROM sys.server_event_sessions 
			WHERE name = 'UnknownAppHosts')
	DROP EVENT SESSION UnknownAppHosts 
	ON SERVER;

-- Create the Event Session
CREATE EVENT SESSION UnknownAppHosts 
ON SERVER 
ADD EVENT sqlserver.login(
    ACTION(sqlserver.client_hostname)
--add filters on the login here.  This would only watch anonymous .Net apps
--	WHERE ([sqlserver].[client_app_name] LIKE '.Net SQLClient Data Provider%')
	WHERE ([sqlserver].client_hostname NOT LIKE '%-MQ-%')
	) 
ADD TARGET package0.histogram
( SET slots = 50, -- Adjust based on expected number of "buckets" needed
	  filtering_event_name='sqlserver.login', 
	  source_type=1, 
	  source='sqlserver.client_hostname' 
)
WITH(MAX_DISPATCH_LATENCY =1SECONDS); 
GO

-- Start the Event Session
ALTER EVENT SESSION UnknownAppHosts 
ON SERVER 
STATE = start ;
GO

-- Parse the session data to determine the host/database.
-- When you stop the session, the records go AWAY, so make sure to run this before that!
SELECT  slot.value('./@count', 'int') AS [Count] ,
        slot.query('./value').value('.', 'varchar(20)')
FROM
(
	SELECT CAST(target_data AS XML) AS target_data
	FROM sys.dm_xe_session_targets AS t
    INNER JOIN sys.dm_xe_sessions AS s 
		ON t.event_session_address = s.address
	WHERE   s.name = 'UnknownAppHosts'
	  AND t.target_name = 'Histogram') AS tgt(target_data)
CROSS APPLY target_data.nodes('/HistogramTarget/Slot') AS bucket(slot)
ORDER BY slot.value('./@count', 'int') DESC

GO

----------------------------------
--WHEN AND ONLY WHEN YOU'RE DONE--
----------------------------------
-- Stop the Event Session
ALTER EVENT SESSION UnknownAppHosts 
ON SERVER 
STATE = STOP ;
GO
-- Drop the Event Session
DROP EVENT SESSION UnknownAppHosts 
ON SERVER;