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How to Detect Empty Password Users

, 13 Aug 2007
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This article describes how to detect empty password users

Introduction

This article describes how to detect empty password users in the Windows NT environment using Visual C++ 6. This method may require the Platform SDK.

Requisite Knowledge

Readers should be familiar with the C++ language and Windows API. This article is so simple that you can understand it even if you are not a professional.

Empty Password Users: Why We Detect Them

Empty password users can destroy local computers because a WORM VIRUS is able to use such accounts to spread itself. When you turn your system on without a password, your system infects within a minute. For this reason, if you can detect empty passwords, you can advise the user to set a password. In the past I searched Google for how to deal with this, but I could not get anything about it. So, I decided to write my own program. This is some simple empty password detection code that runs on Windows NT; it does not support Windows 9x.

What is the Problem?

The first idea is using the LogonUser API. This API can log in a given user name and return a result. The first code example is:

HANDLE hToken = NULL;
BOOL bLoggedOn = ::LogonUser(pszUserName, pszPassword, NULL, 
    LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, &hToken);

if(bLoggedOn) 
{
    printf("Logged On!\n");
} 
else 
{
    printf("Failed\n");
}

However, the first code's problem is that the LogonUser API does not work with an empty password. We cannot call this function with a NULL password or "". In this situation, how can we detect an empty password? The answer is simple: just check the error code. In MSDN, LogonUser returns the error code via GetLastError. So, we can get LogonUser's error by using the GetLastError function. The following code describes how to get the error code of LogonUser.

HANDLE hToken = NULL; 
BOOL bLoggedOn = ::LogonUser(pszUserName, "", NULL, 
    LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, &hToken);
DWORD dwError = GetLastError();

dwError has the error code of LogonUser. LogonUser returns error code 1327 when a user has an empty password. I tested the following code from Windows XP on my own system and it works well.

HANDLE hToken = NULL; 
BOOL bLoggedOn = ::LogonUser(pszUserName, "", 
    NULL, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, 
&hToken);
DWORD dwError = GetLastError();

if(bLoggedOn || dwError == 1327)
{
    printf("Empty Password Logon User: %s\n", pszUserName);
}

History

  • 13 August, 2007 -- Original version posted

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Yonghwi Kwon
Software Developer
United States United States
I started to write software since 1999 and have developed various products including security solutions and system utilities.
 
Microsoft Visual C++ MVP (from 2008 to present)
Website: http://rodream.net

Comments and Discussions

 
SuggestionSuggestion to use in C# Pinmemberfreedeveloper2-Jul-12 11:52 
GeneralDomain user gets locked out PinmemberDuggi18-Dec-07 22:01 
GeneralRe: Domain user gets locked out PinmemberKwon Yong Hwi19-Dec-07 14:35 
GeneralRe: Domain user gets locked out Pinmemberjamalhaider18-Jun-08 19:52 
GeneralRe: Domain user gets locked out PinmemberDuggi22-Oct-08 0:44 
GeneralEach test will add two entries in eventviewer PinmemberRalf Lohmueller5-Sep-07 19:32 
Hi all,
 
nice idea, but:
please be aware that using this method
each test will add two entries in eventviewer
(security events).
I don't know, if administrators like this.
 
btw:
Is it also a possible scenario, that if
an application uses this too often,
a user gets locked out?
(depending on the user/group-policy)
Did someone test this?
 
greetings,
ralf
GeneralError 1327 PinmvpDavidCrow21-Aug-07 3:32 
GeneralRe: Error 1327 PinmemberKwon Yong Hwi22-Aug-07 3:20 
GeneralGreat tip! PinmemberGrump20-Aug-07 23:01 
GeneralRe: Great tip! PinmemberKwon Yong Hwi22-Aug-07 3:19 
GeneralGood one! PinmemberVasudevan Deepak Kumar16-Aug-07 1:59 
GeneralRe: Good one! PinmemberAnand Todkar16-Aug-07 5:01 
General:confused: Wrong code is found Pinmemberj2doll13-Aug-07 19:23 
GeneralRe: :confused: Wrong code is found [modified] PinmemberKwon Yong Hwi13-Aug-07 20:03 
Generalnice one. I will try it PinmemberMichael Sync13-Aug-07 17:06 
GeneralRe: nice one. I will try it PinmemberKwon Yong Hwi13-Aug-07 22:21 
GeneralRe: nice one. I will try it PinmemberMichael Sync14-Aug-07 0:10 

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