XPost: alt.comp.os.windows-11
Stan Brown <
[email protected]> wrote:
From Ars Technica:
In 2012, an industry-wide coalition of hardware and software makers
adopted Secure Boot to protect against a long-looming security
threat. The threat was the specter of malware that could infect the
BIOS, the firmware that loaded the operating system each time a
computer booted up. From there, it could remain immune to detection
and removal and could load even before the OS and security apps did.
Microsoft built a backdoor in UEFI that can be used for software
inventorying, tracking, and by malware. While the executable is stored
in the UEFI, it can't do anything until Windows detects its presence,
and then runs it during startup. Microsoft built in a UEFI rootkit.
A "feature" of UEFI (with Microsoft's involvement) is a program can be specified in the UEFI to run on Windows startup. Despite regulating any startup programs, or scanning for malware, there could sit a call to a
program in the UEFI. It could, for example, be used for starting
execution of tracking software (how the computer is used), or for
software inventorying on workstations. I've only seen it used by
companies that wanted to add usage tracking, location, anti-theft, or inventorying to their workstations. However, it could also be used by
malware, and I don't know if any AVs check for a program load specified
in the UEFI. As I recall, some mobos (Lenovo, Gigabyte, ASUS) use this
trick to run services or diagnostics on Windows startup. The AV should
catch malware for whatever the UEFI program load specifies; that is, the
.exe in UEFI usually calls some other program that runs under Windows.
It is a "feature" only with UEFI. When Windows loads, it has a program (C:\Windows\system32\wpbbin.exe) that runs to determine if the UEFI
specified a start program. The UEFI start program is in one of the ACPI
tables in the BIOS. One trick is to rename the loader program in
Windows called the UEFI Bootkit dubbed BlackLotus.
You can Nirsoft's Firmware Tables View to see the ACPI tables in UEFI.
Look for the "Windows Platform Binary Table" (WPBT). Nirsoft will show
the ACPI table, if it is defined, but won't let you delete it. When I
found out about this, Nirsoft didn't show a WPBT table, but then I have
many options disabled in the BIOS. I also don't have the wpbbin.exe
program (that checks the UEFI for an .exe file to load) in my Windows installation.
Although pundits attempt to tout UEFI, Secure Boot, and other later
security measures as protecting users, there are UEFI Bootkits that
bypass all those measures, even Secure Boot, like BlackLotus.
https://arstechnica.com/information-technology/2023/03/unkillable-uefi-malware-bypassing-secure-boot-enabled-by-unpatchable-windows-flaw/
Those are different beasts than the UEFI program load specified in an
ACPI table that Windows checks if it is defined, and if found will run
the UEFI-specified program. I'm noting the UEFI program load on Windows
launch because refurbs often are company workstations that were leased,
and then disposed of. Companies may employ tracking, location, or
software inventorying that the Windows-loaded UEFI-specified program
will start. You won't find that method listed in, say, SysInternals'
Autoruns. Windows loads, checks the UEFI for the bootkit/rootkit
program, and runs that program under Windows. Since Secure Boot okays
the load of Windows, and since it is a program under Windows that loads
the .exe in the UEFI, Secure Boot won't catch this tactic.
https://eclypsium.com/blog/everyone-gets-a-rootkit/
There are tools to nullify the .exe in the WPBT ACPI table in UEFI by
deleting it from memory before Windows reads the ACPI tables, like:
https://github.com/Jamesits/dropWPBT#from-windows
This removes the WPBT table from system memory, so you have it run as a
startup program (that loads with Windows startup, not until whenever you
log into your Windows account).
For your own computer, you don't want WPBT employed. WPBT started with
Windows 8. Probably the easiest way to disable WPBT is to rename,
delete, or move the wpbbin.exe if it exists on your system. An update
could replace it, so you might want to use Task Scheduler to run a
delete command on every Windows startup. The Github article talks about different methods of disabling WPBT, but they're rather complicated instructions.
--- SoupGate-Win32 v1.05
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