Windows 8 and Windows 10 contain a surprising feature that many users will find unwelcome: PC OEMs can embed a Windows executable in their system firmware. Windows 8 and 10 will then extract this executable during boot time and run it automatically. In this way, the OEM can inject software onto a Windows machine even if the operating system was cleanly installed.

The good news is that most OEMs fortunately do not seem to take advantage of this feature. The bad news is that "most" is not "all." Between October 2014 and April of this year, Lenovo used this feature to preinstall software onto certain Lenovo desktop and laptop systems, calling the feature the "Lenovo Service Engine."

Lenovo's own description of what the software did differs depending on whether the affected system is a desktop or a laptop. On desktops, the company claims that the software only sends some basic information (the system model, region, date, and a system ID) to a Lenovo server. This doesn't include any personally identifying information, but the system ID should be unique to each device. Lenovo says that this is a one-time operation and that the information gets sent only on a machine's first connection to the Internet.

For laptops, however, the software does rather more. LSE on laptops installs the OneKey Optimizer (OKO) software that Lenovo bundles on many of its machines. OneKey Optimizer arguably falls into the "crapware" category. While OKO does do some somewhat useful system maintenance—it can update drivers, for example—it also offers to perform performance "optimizations" and cleaning "system junk files," which both seem to be of dubious value.

Making this rather worse is that LSE and/or OKO appear to be insecure. Security issues, including buffer overflows and insecure network connections, were reported to Lenovo and Microsoft by researcher Roel Schouwenberg in April. In response, Lenovo has stopped including LSE on new systems (the company says that systems built since June should be clean). It has provided firmware updates for affected laptops and issued instructions on how to disable the option on desktops and clean up the LSE files.

The issue was spotted by a poster on our own forums. That poster described some even more undesirable behavior on Windows 7 systems. On those machines, it appears that LSE replaces a Windows system file, autochk.exe (which is used for the boot-time chkdsk filesystem verification and repair process). The bogus autochk.exe then creates system services that fetch files over unencrypted HTTP.

Lenovo's own guidance alludes to the overwriting of system files, but it's not at all clear how this is happening on Windows 7—the Windows capability to run executables stored in firmware appears to be new to Windows 8—or why it's overwriting a system file. We've asked Lenovo about these issues, but the company merely referred us to its statement announcing the discontinuation of LSE and the availability of removal tools. (We suspect that the system in question has more than one way of injecting software into Windows, but more on this shortly.)

In the light of Schouwenberg's bug report, Microsoft recently updated its guidance for the this facility to note that software injected in this way should be written to be secure and that insecure programs are liable to be treated as malware. As for the feature itself, that remains a part of Windows.

And in its own awful way, it's a feature that makes sense. The underlying mechanism is simple enough; the firmware constructs tables of system information when the machine boots. The operating system then examines these tables to, for example, learn what hardware is installed in the machine and how it is connected. This is all governed by a specification called ACPI, Advanced Configuration and Power Interface. Microsoft defined a new ACPI table, the Windows Platform Binary Table (WPBT), that contains information about a firmware-embedded executable. When it boots, Windows looks for a WPBT. If it finds one, it copies the executable onto the filesystem and runs it.

The primary purpose of WPBT is the automatic installation of anti-theft software. This kind of software typically does a couple of things that require online connectivity: it can phone home to check if it's been reported stolen (and brick or otherwise disable itself if it has), and it can phone home to simply report where it is to aid recovery of lost or stolen hardware.

It's reasonably common (though by no means universal) for stolen hardware to have its disk wiped, thereby removing any anti-theft software and limiting the chance of recovery. WPBT provides a solution: even if the disk is wiped and the operating system reinstalled, the firmware can re-establish the software and report that the laptop was stolen.

Believe it or not, this is one of the less invasive anti-theft techniques in use. Anti-theft system LoJack (also known as Computrace) is widely found on business-oriented laptops (including some models from Lenovo). LoJack also injects itself into the operating system even after a clean installation, but the way it does so is rather more underhanded: it includes BIOS code that directly modifies Windows system files—including autochk.exe . Our guess is that LSE uses a similar technique to install itself when booting old operating systems like Windows 7, explaining the overwritten file that our forum poster observed.

In the context of anti-theft, this kind of capability makes sense and is arguably even desirable. The owner of a system should have the power and authority to establish robust protection in the case of theft. LoJack firmware, for example, traditionally ships in a "disabled" state and requires user intervention to enable. But a manufacturer using an anti-theft technique to install crapware feels like an abuse of the capability, especially as LSE was turned on by default.

Lenovo did include a firmware option to disable LSE, though we've seen one report that a system was showing LSE-like behavior but lacked the option to disable it.

It's not clear which other PC manufacturers have taken advantage of the WPBT capability, or in what capacity they've used it. The company that makes LoJack provides a lengthy list of systems that include its firmware, and most or all of them likely use this system. In the meantime, we'd recommend that users of affected systems (a full list of desktops can be found here and laptops here) update their firmware to remove LSE and then run Lenovo's LSE removal tool to clean the files from their disk.

Listing image by Cory M. Grenier