Cannot connect to local SQL Server 2012 via SSMS - sql-server

Question

I'm trying to connect to my local SQL Server 2012 via SSMS, but I didn't make it. I got error message :
Cannot connect to EB-OR1007724.
Additional information:
Login failed. The login is from an untrusted domain and cannot be used with Windows authentication. (Microsoft SQL Server, Error: 18452)
Please notice that I'm using a company computer with many restrictions. After trying several things, but I stilled didn't make it.
Check services are running. All related SQL Server Services are running using Local System as Log On. They're
SQL Full-text Filter Daemon Launcher (MSSQLSERVER), started (PID=2100)
SQL Server (MSSQLSERVER), started (PID=2424)
SQL Server Agent (MSSQLSERVER), started (PID=320)
SQL Server Browser, started (PID=4376)
Check ports' status. The port :1434 is listened by localhost 127.0.0.1.
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\xxxxxxxx>netstat -ano
Active Connections
Proto Local Address Foreign Address State PID
...
TCP 127.0.0.1:1434 0.0.0.0:0 LISTENING 2424
TCP [::1]:1434 [::]:0 LISTENING 2424
UDP 0.0.0.0:1434 *:* 3080 1016
UDP [::]:1434 *:* 3080
Check firewall roles. I've created an inbound rule to allow TCP connection to port :1433 and :1434, which can be accessed for all connections by anyone.
Check hosts config. The hosts configuration file hosts has been modified to identified 127.0.0.1 as localhost. This file is located at folder C:\Windows\System32\drivers\etc.
Check availability of other SQL Server services. I can connect to the local SSAS services using my windows authentication.
Check AD Server status. The problem might be caused by a down Active Directory Server. Even though I don't have access to Active Directory Domains and trusts due to company policy, I'm sure that the AD server works, because I can connect to the local SSAS services using my windows authentication.
Check instance name. As you can see, the instance is called MSSQLSERVER, so perhaps I should explicitly mention it when I connect via SSMS ? These are what I've tried in Server name:
EB-OR1007724, error 18452
EB-OR1007724\, error 18452
EB-OR1007724\MSSQLSERVER, error 87
.\MSSQLSERVER, error 87
.\, error 18452
., error 18452
Now I'm really upset upon the result. Please help T_T
Error list
Error 87
Cannot connect to EB-OR1007724\MSSQLSERVER.
Additional Information:
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 25 - Connection string is not valid) (Microsoft SQL Server, Error: 87)
The parameter is incorrect.
Error 18452
Cannot connect to EB-OR1007724.
Additional information:
Login failed. The login is from an untrusted domain and cannot be used with Windows authentication. (Microsoft SQL Server, Error: 18452)
For your information, there's a related question on stackoverflow.

Answer 1

Cause
The problem might be caused by company security programs, defined on the network. Since the local service MSSQLSERVER is not a company official service, the Active Directory (AD) Server refuses to provide authentication credentials. (Obviously, this is my hypothesis. ^^)
Solution
As for the solution, I use SQL Server Authentication instead of Windows Authentication to login. In order to do that, make sure your server is running under the Mixed Mode (Windows authentication and SQL Server authentication). This can be configured during the SQL Server 2012 installation, step Database Engine Configuration.
The login is sa (system administrator) and the password is what you've defined previously.
Once connected, you should add new login(s) properly for different usages. As mentioned by Panagiotis Kanavos:
connecting as sa is considered a serious security problem, not a solution of any kind. It should never, ever be attempted in production systems