What software can I use to remove malware?

1) I get occasional pop-ups about using ‘Mac Cleaner’ and others

2) I have several devices, including an iMac, MacBook Air, iPad and iPhones. They all share an iCloud Account. Even the newest devices show have had pop-ups suggesting that there is(are) a shared contaminant(s). Is there a way to search/clean all files on the iCloud or should they all be quarantined and taken down one by one, if one would ever have that time ?

3) How do you cleanup a hard drive back-up from these malware so as not to recontaminate the device(s)?

Any help is appreciated. Thanks