Help with Malware

I have many sites on my hosting account and some of them are wordpress, I have received reports from google that I had malware in some of my sites, I have gone through a bunch of times to remove anything unusual, I have reset passwords, and tried a bunch of different plugins, the malware keeps coming back.
I talked to webserve and was told that purchasing site lock will protect my whole hosting account which clearly it is not.

What is the best plugin for malware removal and blocking? Any advice is much appreciated!