Prevx backs off claims that Microsoft patches are contributing to a Black Screen of Death condition being experienced by some Windows users.
Security vendor Prevx has narrowed
down the cause
of a "Black Screen of Death" condition affecting
According to Prevx, the
issue does not appear to be connected to patches issued by Microsoft. In
an update this evening to a company blog, the company said the issue seems to
be "related to a characteristic of the Windows Registry related to the storage
of string data."
"In parsing the Shell
value in the registry, Windows requires a null terminated 'REG _SZ' string," blogged Jacques
Erasmus of Prevx. "However, if malware or indeed any other program modifies the
shell entry to not include null terminating characters, the shell will no
longer load properly, resulting in the infamous Black Screen with the PC
showing only the My Computer folder."
had reported previously
that some Windows users were experiencing a Black
Screen of Death, and laid the blame in part at the feet of Microsoft patches,
specifically KB915597 and KB976098. Erasmus, however, wrote that the patches
are no longer considered to be a contributory factor.
"Having narrowed down a specific trigger for this condition we've done
quite a bit of testing and re-testing on the recent Windows patches including
KB976098 and KB915597 as referred to in our previous blog," he wrote.
"Since more specifically narrowing down the cause we have been able to
exonerate these patches from being a contributory factor."
Christopher Budd, communications lead for Microsoft Security Response
Center, added that Microsoft's own investigation had discounted their November
security patches as being tied to the problem.
"We've conducted a
comprehensive review of the November Security Updates
, the Windows Malicious Software Removal Tool
, and the
non-security updates we released through Windows Update in November," he
blogged. "That investigation has shown that none of these updates make any
changes to the permissions in the registry. Thus, we don't believe the updates
are related to the 'black screen' behavior described in these reports."
"We've also checked with
our worldwide Customer Service and Support organization, and they've told us
they're not seeing 'black screen' behavior as a broad customer issue," he
In response to the
problem, Prevx released
a free tool
to fix the most common causes of the issue the company has
seen. Customers concerned about the issue can also contact Customer
Service and Support
for free assistance.