As per http://www.liutilities.com/products/wintaskspro/processlibrary/dllhost/ -
dllhost.exe is a part of the Microsoft Windows Operating System. The dllhost.exe file manages DLL based applications. This program is important for the stable and secure running of your computer and should not be terminated.
Author: Microsoft Corp.
Part Of: Microsoft Windows Operating System
System Process: Yes
Background Process: Yes
Uses Network: No
Hardware Related: No
As per http://blogs.msdn.com/robgruen/archive/2004/08/18/216685.aspx
XP SP2 Issues – Using the System Provided Surrogate (dllhost.exe)
DLLHost.exe can be used as a surrogate host for COM servers that are exposed via DCOM/COM+. On XP SP2 the situation may arise that you need to allow your surrogate hosted DCOM app to be accessible from outside of the personal firewall. Typically you would add your process to the firewall white list (trusted apps that are allowed access through the firewall) but the problem with doing this for dllhost.exe is that this opens the firewall for your DCOM server and any other application running under dllhost.exe. You may or may not want to do this.
Continue reading for PROS and CONS info.
From a ZA user research:
Process name: DCOM DLL host process
The COM+ hosting process controls processes in the Internet Information Services (IIS) and is used by many programs. It loads .NET Runtime for example. There can be multiple instances of DLLhost.exe.
Note: The dllhost.exe file is located in the c:\windows\System32 folder. In other cases, dllhost.exe is a virus, spyware, trojan or worm!
Virus with same name: Worm/Nachi.A.1 - antivir.de
Zone Alarm Pro snagged an outbound transmission by COM Surrogate. It says it's bad and I shouldn't allow it, so I listened!
The program is "dllhost.exe" and it is located in \\system32.
I use (almost) every known spyware removal (XPHome, AdAware, Spybot, Hosts file, Spyware Blaster and Guard, amongst others) innoculator, etc. How did this 'thing' get in and how do I remove it?