Synopsis: The mechanics of BIOS password locks present in current generation laptops are briefly outlined. Trivial mechanisms have been put in place by most vendors to bypass such passwords, rendering the protection void. A set of master password generators and hands-on instructions are given to disable BIOS passwords.
When a laptop is locked with password, a checksum of that password is stored to a so-called FlashROM – this is a chip on the mainboard of the device which also contains the BIOS code and other settings, e.g. memory timings.
For most brands, this checksum is displayed after entering an invalid password for the third time:
The dramatic ‘System Disabled’ message is just scare tactics: when you remove all power from the laptop and reboot it, it will work just as before. From such a checksum (also called “hash”), valid passwords can be found by means of brute-forcing.
The bypass mechanisms of other vendors work by showing a number to the user from which a master password can be derived. This password is usually a sequence of numbers generated randomly.
Some vendors resort to storing the password in plain text onto the FlashROM, and instead of printing out just a checksum, an encrypted version of the password is shown.
Other vendors just derive the master password from the serial number. Either way, my scripts can be used to get valid passwords.
A few vendors have implemented obfuscation measures to hide the hash from the end user – for instance, some FSI laptops require you to enter three special passwords for the hash to show up (e.g. “3hqgo3 jqw534 0qww294e”, “enable master password” shifted one up/left on the keyboard). Some HP/Compaq laptops only show the hash if the F2 or F12 key has been pressed prior to entering an invalid password for the last time.
Depending on the “format” of the number code/hash (e.g. whether only numbers or both numbers and letters are used, whether it contains dashes, etc.), you need to choose the right script – it is mostly just a matter of trying all of them and finding the one that fits your laptop. It does not matter on what machine the script are executed, i.e. there is no reason to run them on the locked laptop. This is an overview of the algorithms that I looked at so far:
The .NET runtime libraries are required for running the Windows binary files (extension .exe). If the binary files (.exe) don’t work out for you, install Python 2.6 (not 3.x) and run the .py script directly by double-clicking them. Make sure that you correctly read each letter (e.g. number ‘1’ vs letter ‘l’).
Also, be aware that some vendors use different schemes for master passwords that require hardware to be reset – among them are e.g. IBM/Lenovo. If you find that your laptop does not display a hash or the scripts do not work for you for whatever reason, try to:
- use a USB keyboard for entering the password for avoiding potential defects of the built-in keyboard,
- run CmosPwd to remove the password if you can still boot the machine,
- overwrite the BIOS using the emergency recovery procedures. Usually, the emergency flash code is activated by pressing a certain key combination while powering on the machine. You also need a specially prepared USB memory stick containing the BIOS binary. The details are very much dependent on your particular model. Also, be aware that this can potentially brick your device and should only be done as a last measure.
- Some dell service tags are missing the suffix – just try the passwords for all suffices by adding -595B, -2AB7 and -D35B to your service tags.
- Some older laptop models have service manuals that specify a location of a jumper / solder bridge that can be set for removing the password.
I have used the word script frequently in the post. To see the one of the script use to crack the bios password of Fujistu-Siemens. Click here . This script is in Python Programming Language so u need to have a compatible compiler or you may use the Notepad just to view the codes.
If none of the above methods work, please use the vendor support. Please understand that my motivation for reverse-engineering comes from a personal interest – I will not accept offers to look at the specifics of certain models.