Do you have any Patches for Mcafee 8.7 installed? If not, try the latest Patch5, which resolves several "DAT Update Performance Issues". You can download it in the download section with your GRANT number.
We are running patch 3 right now.
Do you know why my on access scan file has some changes on everyday at 1:20 PM? Thats the time when I see the DAT version changes as well.
Patch 3 caused a significant subset our users to start really moaning when DAT update time came around. We're moving to patch 5 and hoping that does indeed allow us to move a DAT update intraday again without rendering older machines nearly unusable for a few minutes.
Look in your ePO in the system tree where one of the systems exhibiting this behavior lives. Look at the client tasks, and you'll probably find a Product Update task scheduled daily--and the time will probably look pretty familiar. That's what typically causes your DAT's to get updated and determines when... unless you don't have one set, and I think perhaps VirusScan might have a fallback default to go out to mcafee.com to go get its dat updates (not sure on this...we push ours from ePO on a time we control).
A DAT update does indeed cause entried to be added to the access protection log, on-access scanner log, and probably several other logs. That's entirely normal behavior.