Threat Descriptons



Category :


Type :


Aliases :

Delf.fz, Trojan-PSW.Win32.Delf.fz


Trojan-PSW.Win32.Delf.fz is a delphi application that drops and loads a password stealing component on infected system.


Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

Trojan-PSW.Win32.Delf.fz is a PE executable written in delphi. The trojan file is unpacked and about 51 kilobytes long.

Installation to system

When the trojan file is executed, it makes a copies itself as 'explorer.exe' to Windows system folder. It then adds the following registry key to ensure it will be started next time Windows is started:

[HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell]
"Explorer.exe" = "C:\Windows\system32\Explorer.exe"

The trojan also adds an entry to the win.ini file using the Windows API call WritePrivateProfileStringA from the Kernel32.dll. The entry will look like this:


As win.ini is not supported by Windows NT, 2000 and XP, on these operating system the changes will be added to the Registry.

The trojan also drops a file 'htdll.dll' from its resource to Windows system folder. This DLL is is the password stealing component.


Trojan-PSW.Win32.Delf.fz activates the dropped DLL which starts to monitor Internet Explorer for account information (usernames, passwords). The DLL is activated using a fixed URL that is used to later send collected information to trojan author. The DLL can also send collected information using emails.

The trojan tries to kill several firewalls and other security related software in the installation phase to make sure the DLL can connect to remote server.

The trojan also tries to download and activate additional component during the installation. At the time of this writing, this component is not available.

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