If you are looking at your Event Log and you are seeing this message repeated thousands of times you would naturally become concerned. Your next step might be to try to figure what this means so you may launch an internet search to try to find an answer.
You may find the following post on the vPro Expert Center. This post is from 2009 (it is now 2013) and states that this is seen when you change the admin password (for, example from the Web UI interface) to something different than the ME password (the password that you enter to get into the MEBx. The post states that the system is working as designed. This post does not say how often this event occurs (1,2, thousands of times?) Anyone who sees this alert occuring repeatedly all day, should be concerned.
Is your system actually "under attack?" Probably not.
One thing that can cause this event is if your system does not have the right version of drivers installed for the ME Interface (MEI driver) and for the LMS service. For example, if your Intel AMT client is an Intel AMT 9 system, you need to have drivers and software that are compatible with Intel AMT 9.
You can look at section 6 of the Start Here Guide to see which drivers an Intel AMT system requires. If you detemine that this is why your system is generating this event, you will need to go to your OEM's website, get the correct drivers/software and install them. (You may also have a DVD that came with your system that has all the drivers, but they may not be the latest versions.)
You will also need to uninstall the MEI driver and LMS software that are not compatible with your system.
A driver mismatch can happen if you take an image from an older vPro system and apply it to a newer system. (This will overwrite the drivers that came with the system when it was purchased.)
Note also that you cannot upgrade the ME FW to a newer release, for example, a system that has the ME 8 hardware cannot be upgraded to run the ME 9 release. You can only upgrade to newer versions within the same release. Consequently, if you have an AMT 8 system, you would not be able to simply install release 9 of the MEI driver and LMS software because it will not be compatible with the hardware.