McAfee’s definitions for today, 5958 dated April 21st, has a false positive that is detrimentally affecting computers around the world. The definitions are detecting C:WindowsSystem32svchost.exe as W32/Wecorl.a virus. Svchost.exe, as you may be aware is a critical Windows files that is required for network/Internet communication to work.
More info as the story breaks and I have a second to sit down.
To get around the ‘in use’ message and repair things, I’ve been following this process:
- Boot up into safe mode.
- Copy the extra.dat to C:program filescommon filesMcafeeengine
- Go to C:WindowsSystem32 and move svchost.exe to the desktop (or somewhere temporarily).
- Inside McAfee VirusScan Console go into the Quarantine Manager and restore all of the instances from today.
Machine is then Ok for normal use.
McAfee’s “DAT” file version 5958 is causing widespread problems with Windows XP SP3. The affected systems will enter a reboot loop and loose all network access. We have individual reports of other versions of Windows being affected as well. However, only particular configurations of these versions appear affected. The bad DAT file may infect individual workstations as well as workstations connected to a domain. The use of “ePolicyOrchestrator”, which is used to update virus definitions across a network, appears to have lead to a faster spread of the bad DAT file. The ePolicyOrchestrator is used to update “DAT” files throughout enterprises. It can not be used to undo this bad signature because affected system will lose network connectivity.
The problem is a false positive which identifies a regular Windows binary, “svchost.exe”, as “W32/Wecorl.a”, a virus. If you are affected, you will see a message like:The file C:WINDOWSsystem32svchost.exe contains the W32/Wecorl.a Virus. Undetermined clean error, OAS denied access and continued. Detected using Scan engine version 5400.1158 DAT version 5958.0000.
McAfee released an updated DAT file, and an “EXTRA.DAT” file to fix the problem. An EXTRA.DAT file is a patch to just fix the bad signature. McAfee’s support web sites currently respond slowly and are down at times, likely due to the increased load caused by this issue.
Several readers reported that this procedure worked to recover:
1 – Boot the system in “Safe Mode”
2 – copy extra.dat in c:/program files/common files/mcafee/engine
3 – reboot.
If you lost “svchost.exe”, then you need to copy it back to c:/Windows/system32/svchost.exe while in safe mode. This fix has to be applied locally at the workstation. However, it may be possible to do this remotely if your workstations support Intel’s “vPro” technology. We should have a link to instructions shortly.
Additional information from McAfee: http://community.mcafee.com/thread/24056?tstart=0
McAfee Knowledgebase Article: https://kc.mcafee.com/corporate/index?page=content&id=KB68780
EXTRA.DAT file: http://home.mcafee.com/VirusInfo/VirusProfile.aspx?key=265240
McAfee has deployed a SuperDAT that is having even better luck at reviving machines. Download the SuperDAT to fix this problem to a USB memory stick and then boot the broken computer into safe mode and run the SuperDAT. After it completes (takes about 2-3 minutes), reboot and the computer will likely be repaired.
If you get an odd message about the shutil.dll file missing like I did a few times (out of dozens of machines) copy the shutil.dll file from a working computer at c:program filesmcafeevirusscan enterpriseshutil.dll to the same location on the broken machine in Safe Mode.