Skype Reads Your BIOS and Motherboard Serial Number

Users of Skype that run 64-bit versions of Windows like me probably have noticed that when starting Skype, the following dialog box appears:

The program or feature “\??\C:\Documents and Settings\Myria\Local Settings\Temp\12\” cannot start or run due to incompatibility with 64-bit versions of Windows. Please contact the software vendor to ask if a 64-bit Windows compatible version is available.

Well, that’s weird. Skype’s trying to run a .com file, which won’t work on Win64 because there’s no NTVDM. Let’s try opening it in Hex Workshop. Access denied? OK, I’ll terminate Skype to read it. Still can’t?! This thing is really starting to annoy me. I’ll use WinDbg to terminate winlogon.exe to force a kernel panic. I reboot and NOW I can read the damn file.

An unreadable executable file coming from Skype sounds interesting, so I look at it. It’s 46 bytes long. For copyright reasons I can’t post the file or a complete disassembly. However, I can describe the program in terms of 16-bit DOS C:

int main(void)
fwrite((const void far*) 0xF0000000, 1, 0xFFFF, stdout);
fwrite((const void far*) 0xF000FFFF, 1, 1, stdout);
return 0;

It’s dumping your system BIOS, which usually includes your motherboard’s serial number, and pipes it to the Skype application. I have no idea what they’re using it for, or whether they send anything to their servers, but I bet whatever they’re doing is no good given their track record.

In 32-bit Windows NT, including Vista, the kernel permits NTVDM to make a read-only mapping of the BIOS at address 000F0000. This allows DOS programs running under NTVDM to make use of the BIOS. That’s how this 46-byte program is capable of sending the BIOS to the Skype application, and also explains why they use this mechanism to begin with.

If they hadn’t been ignorant of Win64′s lack of NTVDM, nobody would’ve noticed this happening.

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297 Responses to “Skype Reads Your BIOS and Motherboard Serial Number”

  1. [...] klientas? Susidomėjusiems – Firefox profilo skaitymas nėra vienetinis atvejis. Skype aktyviai nuskaito BIOS nustatymus, kurie apskritai neturėtų turėti naudingos informacijos tokiai programai, kaip Skype. Skype [...]

  2. [...] Skype Reads Your BIOS and Motherboard Serial Number – заметка в йНОго, разоблачающая махинации, скрыто проделываемые Skype, читающим BIOS и серийный номер материнской платы: [...]

  3. El Novi says:

    Привет всем!
    А почему собственно осНи программа вычисляет адреса йиОса и другие параметры системы Она вредить собирается? Она может делать обратную суППу иС части йиОса (напр. 1024байта) – Он ведь но изменяется программно (ну иНи почти) – почему-бы но использовать эти данные для аутентификации уникального ключа который используется для шифрования.

  4. [...] and apparently, Skype Reads Your BIOS and Motherboard Serial Number upon startup. Now thats a nasty backdoor and privacy threat. What better way to catalog the [...]

  5. Peps says:

    Они могут накапливать в своей базе серийник вашей мамки + твой логин. А значит следить какие логины использовались на одном компе.
    Сам факт какого-то постороннего кода уже подозрителен.. Что-то здесь не то!

  6. Прикольный биос получается!

  7. Yea and itunes installed something similar. I bet everything does

  8. ?????? says:

    I bet everything does.Yea and itunes installed something similar. I bet everything does

  9. Frak Jovine says:

    Thankfully this was solved a while back, but it could be re-engineered elsewhere. Nice post!

  10. [...] Skype Reads Your BIOS and Motherboard Serial Number – ??????? ? ?????, ????????????? ?????????, ?????? ????????????? Skype, ???????? BIOS ? ???????? ????? ??????????? ?????: [...]

  11. Borislav Sabev says:

    I;d rather they didn’t do this, but here:
    they explain why. Still, the Privacy Agreement is met…

    “Of course, in line with our Privacy Agreement, Skype does not retrieve any of this data. It is only used by the EasyBits software to ensure that plug-in use complies with the appropriate license token or key.”

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    In this day and age its always good to be on the alert. We all benefit in some way when knowledge is power. Power to people i say! It will always keep these huge companys on the alert, instead of big brother watching us, its our turn to keep watch on them. Good post!

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