How to fix Dllhost.exe errors?

Dllhost.exe, Windows background process as it is, is not as familiar to PC users as svchost.exe, people start to post questions and suspicions on dllhost.exe and some even consider it is a virus due to the following scenarios occur to be accompanied by dllhost.exe running process:

CPU usage stays over 70% on average and spikes to over 90% from time to time with multiple dllhost.exe running in the Task Manager.
A few of software is installed on the computer consumed by dllhost.exe.
Opening a downloaded folder prompts error message telling that “C:\Windows\system32\DllHost.exe” triggers buffer overflow and that it is using up about 7500K of the internal storage.
McAfee warns that the buffer overflow caused by dllhost.exe can damage valuable files in the problem computer (if it ever happens) and damage it.

Dllhost.exe’s Functions

As its name suggests, dllhost.exe is applied in managing DLL so that the operating system becomes capable of coordinate build-in controls, drivers, software and hardware appropriately and the OS becomes stronger in resisting virulent infiltration equipped with timely update. It can now be told that dllhost.exe plays an important role in normal operation and it is one of the components of Windows OS. Generally speaking, dllhost.exe occupies 3664k.


Reasons for High Consumption by Dllhost.exe and Its Damages

Though dllhost.exe manages dll operation, it is not usually caught running in Task Manager. In fact, dllhost.exe only appears when COM+ assembly program is activated. Therefore, dllhost.exe can also be considered as COM agent to run Web and FTP server under Windows. Besides, dllhost.exe owns the capability of coordinating dll operation, some attackers have put their eyes on it for malicious affection. So roughly there are two reasons to incur dllhost.exe problem.

Reason NO. 1:
MDAC loads Microsoft ACCESS(es) that corrupt(s) when reading and writing. ASP thread becomes blocked thereafter. Other threads have to do nothing but wait, leading to IIS deadlock. Therefore, all CPU is spent on dllhost.

Feature:
CPU stays 100% and never comes down until the restart of IIS service. However, CPU spikes to 100% again a little while after the restart.

Damages:

Browser would crash.
Some more unfamiliar web page error might emerge to stop surfing.

Reason NO. 2:
Some program didn’t close Database after establishing an object. CPU will be consumed more to server day by day.

Damages:

Computer would freeze occasionally.
It takes longer to load the intended web page.

Reason NO. 3:
Infections, worm particularly, replicate themselves in a large number to occupy plenty of computer resource or affect exchange server to keep anti-virus busy, leading to highly consumed CPU.

Damages:

Email accounts might fall into the utilization of spreading virulent codes.
Computer slows down in operation.
Backdoor might be brought into being for additional infiltration.
Web vulnerability can be triggered to be exploited readily by other destructive infections.
Stored information can be collected without knowledge.
Error message may occur.

Reason NO. 4:
Problems happen to thumbnail previews because of some bug that has been found on some dll file of certain program. It is good habit to update installed patches, drivers and the like. However, it is not recommended to install an object that has not been fully tested as bug can be found and malfunction would happen.

Damages:

Error message may occur.
Computer may get stuck in the middle of operation.

How to Fix High CPU Consumption by Dllhost.exe Process

Situation One – IIS deadlock results in high consumption by dllhost.exe.
(tip: such procedure needs patience and carefulness so as to find out guilty files one by one.)

Step1. enable “Find deadlock module” to set “wblock” as “yes” and set file directory, d:\test for example, and “logblock.htm” will be generated under log catalogue.

Step2. restart IIS thereafter, ACCESS file that’s loaded in the end will be recorded in “logblock.htm”.

Step3. check the last 10 ACCESS files (“**COUNT.MDB” and the like) recorded in “logblock.htm” if CPU rises high again.

Step4. move counter files that you suspect to be culprit to Dustbin temporary.

Step5. restart IIS to see if CPU rises again.


Situation Two – persistent request arouse high consumption by dllhost.exe.

Step1. hold and press Win key and R key at once to bring up Run box.
win+r key combination

Step2. type in “iisreset -stop” and hit Enter key.


Situation Three – virus affection brings to high consumption by dllhost.exe.

Step1. record the flagged directory of the detected infection.

Step2. show hidden file and folder and remove any folders named after the virus name in the detected directory.

Step3. navigate to C:\windows\winstart.bat, C:\windows\wininit.ini and C:\windows\Autoexec.bat to remove any suspicious items.

Step4. browse to C:\Windows\System32 to remove any suspicious items.


Situation Four – thumbnail previews lead to high consumption by dllhost.exe.

Step1. restore to the previous version of the file you just updated right prior to the occurrence of dllhost.exe problem.

Step2. delete the file that causes computer freeze temporary in the middle of the download.

Step3. disable thumbnail preview, which is not recommended as disable it would result in invisible movie and other media files.



Final

Knowledge Supplement
Dllhost.exe was published by Microsoft Corp to be located under C:\Windows\system32\dllcache and C:\Windows\winsxs\(for Win7 and Vista) rather than C:\Windows\system32\wins. Dllhost.exe situated in other files under local disks should raise suspicion. What’s more, C:\Program Files\Microsoft Office\media\dllhost.exe has been identified to be virus.

Attention
The above instructions are mainly to help people with high CPU consumption by dllhost.exe running process. If dllhost.exe error persists after the completion of the above instruction, the file may have been corrupted. If it is the case, one should go to reputable .dll file web sites to download and install dllhost.exe for recovery.