This is way late I know, but I am posting for the benefit of anyone who might happen on this thread as I did.
I had to uninstall avast mobile security from my old android phone because it was slowing my phone down too much. I forgot about the extra security it had installed when I first got mobile security. but here is what I found.
1)IF avast is installed through rooted, you can use the uninstall wizard,
2)f not, you have to uninstall the "disguised" app that installs with the unrooted install. I understand that it gives a different name for each device on installation, or perhaps it has a set of names. In my case it was "rdp bridge"
since my device was unrooted at install (I waited until after warranty was over to root), I did not have the option of using the "uninstall wizard" that is "built in" to the app.
I had to"
1) uninstall avast through the app manager
2) uninstall the "disguised security app ("RDP bridge") through the app manager.
I assume you will have to know/remember the name it gives the hidden app to find it.
I chose to use titanium backup to uninstall.
This freed up my space and stopped the rest of the resource hogging that avast seems to do on my older device.
I hope this helps anyone who comes across this in the future.