Syskey

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title: "Syskey" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["cryptographic-software", "microsoft-windows-security-technology", "windows-administration"] description: "Discontinued Windows NT component" topic_path: "technology/operating-systems" source: "https://en.wikipedia.org/wiki/Syskey" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Discontinued Windows NT component ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/be/Syskey_screenshot.png" caption="Screenshot of the Syskey utility on the [[Windows 8.1]] operating system requesting the user to enter a password."] ::

The SAM Lock Tool, better known as Syskey (the name of its executable file), is a discontinued component of Windows NT that encrypts the Security Account Manager (SAM) database using a 128-bit RC4 encryption key.

Introduced in the Q143475 hotfix for Windows NT 4.0 SP3, the tool was removed in Windows 10's Fall Creators Update in 2017 because its method of cryptography is considered insecure by modern standards and the fact that the tool has been widely employed in scams as a form of ransomware. Microsoft officially recommended use of BitLocker disk encryption as an alternative.

History

Introduced in the Q143475 hotfix included in Windows NT 4.0 SP3, Syskey was intended to protect against offline password cracking attacks by preventing the possessor of an unauthorized copy of the SAM file from extracting useful information from it.

Syskey can optionally be configured to require the user to enter the key during boot (as a startup password) or to load the key onto removable storage media (e.g., a floppy disk or USB flash drive).

In mid-2017, Microsoft removed syskey.exe from future versions of Windows. Microsoft recommends using "BitLocker or similar technologies instead of the syskey.exe utility."

Security issues

The "Syskey Bug"

In December 1999, a security team from BindView found a security hole in Syskey that indicated that a certain form of offline cryptanalytic attack is possible, making a brute force attack appear to be possible. Microsoft later issued a fix for the problem (dubbed the "Syskey Bug"). The bug affected both Windows NT 4.0 and pre-RC3 versions of Windows 2000.

Use as ransomware

Syskey is commonly abused by technical support scammers to lock victims out of their own computers in order to coerce them into paying a ransom. It is also used against such scammers by scambaiters as a way to disrupt their fraudulent operations.

References

References

1. (2015-04-06). "Enable Syskey To Protect Windows From Password Cracking". Technig.
2. (12 December 2017). "Features that are removed or deprecated in Windows 10 Fall Creators Update". [[Microsoft]].
3. (20 October 2017). "Syskey.exe utility is no longer supported in Windows 10 version 1709 and Windows Server version 1709". [[Microsoft]].
4. (8 January 2018). "How to use the SysKey utility to secure the Windows Security Accounts Manager database". [[Microsoft]].
5. "Syskey.exe utility is no longer supported in Windows 10, Windows Server 2016 and Windows Server 2019".
6. Sabin, Todd. (December 16, 1999). "bindview.syskey.txt". [[Packet Storm]].
7. Khanse, Anand. (March 9, 2012). "Use SysKey Utility to lock Windows computer using USB stick". The Windows Club.
8. (10 April 2013). "SOLUTION: "This is Microsoft Support" telephone scam – Computer ransom lockout". Triple-S Computers.
9. (17 November 2014). "Tech support company with workers in India claims its 'good name' being ruined by scammers".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::