SQL Server – Resolving SQL Error 18456 Access Issue

loginsSecuritysql server 2014

SQL Server Login is failing for one user where as others can access.

I can see login in list of xp_logininfo members for that particular group in SQL Server Security

Mixed Mode is enabled (Both SQL & Windows Login)

But still getting

Login failed for user 'Domain\Username'. Reason: Could not find a
login matching the name provided. [CLIENT: ]

Best Answer

Cannot access SQL Server - SQL Error 18456

You need to figure out what user does have rights to SQL server. Usually this is the user that you logged in with when you installed SQL Server or the user that is the default administrator on the computer.

I am assuming you have windows server 2012 and above.

I am write down some tricks to short out the Microsoft SQL Server , Error : 18456.

1. Launch Server Manager – Start – Click Server Manager . In the upper right corner, click Tools, then Computer Management. Expand Local Users and Groups (Under Computer Management-System Tools) then click Users

Notice under Description… There is a Built-in account for
administering… This is very likely an account that has access to SQL
server. Try logging onto windows with that account that is Built-in
account for administering then we can grant rights to the user you
want to use to login to SQL Server.

Now that you are logged into Windows with an account that has access
to connect to SQL Server, Let’s go in and grant rights to the user
that you want to be able to use to access SQL Server.

2. Launch SQL Server Management Studio again and you should be able to Connect. Expand your ServerName, then Expand Security, then Logins. Click Logins

Right-Click Logins Select New Login…

Click the Search Button

Type in the Windows User Name you would like to add as an SQL
Administrator then click Check Names (or you can click advanced and
select from a list) 

Click Server Roles in the left pane; then turn on the sysadmin
checkbox, then click OK.

You can then confirm you have sa rights by double-clicking the user
name in the left Object Explorer and clicking on Securables.

Now you can log out of Windows, login as the user you just granted
rights to and all should work fine.

For your further ref : Here

Related Solutions

SQL Server 2012 – Error 9512 When Modifying User Login

Sounds like you have a DDL trigger that is set to listen for ALTER_LOGIN events, and is trying to pass EVENTDATA() directly to some remote procedure.

Check for this using:

USE master;
GO
SELECT OBJECT_DEFINITION([object_id]) 
  FROM sys.server_triggers
  WHERE OBJECT_DEFINITION([object_id]) LIKE N'%ALTER[_]LOGIN%';

It could also be a database-level DDL trigger that listens for ALTER_USER:

USE the_relevant_database;
GO
SELECT OBJECT_DEFINITION([object_id]) 
  FROM sys.triggers
  WHERE parent_class = 0
  AND OBJECT_DEFINITION([object_id]) LIKE N'%ALTER[_]USER%';

Azure VM Security – Many Failed Login Attempts Logged

Is the TCP port SQL Server is listening on open globally?

If so, yes I'd be concerned. If there is a password that can be brute-forced or guessed, or an exploit that allows someone to bypass authentication, eventually your database could be compromised. You'll also be vulnerable to attacks that don't require access, such as someone filling up the drive that that has SQL Server error logs on it by creating many failed logins every second.

If the TCP port is open to the internet, the unwanted login attempts are normal. Based on my experience working at ISPs and hosting companies, a machine that's exposed to the internet will get probed on well-known ports all day (and port scanned periodically) if traffic isn't being dropped by a firewall.

On the other hand, if you have restrictive firewall rules that explicitly allow 124.117.233.94 through, it's likely that one of your customers or colleagues at that address has had a computer compromised.

You can currently read about controlling traffic to Azure Virtual Machines here. A good practice is to drop everything by default and explicitly allow only the traffic you want. Perhaps someone else will edit this to add further information.

Best Answer

Related Solutions

SQL Server 2012 – Error 9512 When Modifying User Login

Azure VM Security – Many Failed Login Attempts Logged

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