Reverse Engineer Your BIOS

wooden laptop

[th0mas] has a fun guide to modifying the boot image in your BIOS. This could very easily brick your laptop, but it’s interesting to see how it’s done. He starts by dumping the plain text strings. The magic number for bitmap format appears in the file so he copies a large chunk of data starting at that point. th0mas opens this in MSPaint to maintain the format. After modifying the image it’s placed back in the BIOS file and a couple checks are performed to make sure only the image data has changed. The final section involves running the flash utility in a debugger to find where it checks the CRC. By modifying the program he can then flash the image without the program complaining.

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