The second app is from the same clever people who make KnockKnock, and it's called BlockBlock. This runs in the background of your Mac via a menu bar icon and monitors all the locations in which persistent apps install themselves. If any app attempts to install persistently then a pop-up dialog box will appear telling you, and it's down to you whether you allow it or ban it. Again, BlockBlock is not an anti-malware tool so doesn't know what's legitimate or not. That's for you to work out. But as forms of malware protection both KnockKnock and BlockBlock are pretty darned effective.
Scan for malware
Although it's true there's more malware targeting Macs, we're still nowhere near the tidal wave that Windows users face on a daily basis. Because of this, and because OS X/macOS already features a powerful, always-running yet invisible anti-malware tool called Xprotect, we reckon that antimalware software is still not a standard requirement for a Mac.
However, for peace of mind you can occasionally fire-up an app like Bitdefender Virus Scanner, which simply scans through your files in order to uncover malware. Unlike Windows antimalware apps, it doesn't install any system monitoring software that can slow the computer down. The best news is that Bitdefender Virus Scanner is free and very easy to use. Be aware that it also finds and reports Windows malware, though. For example, scanning my system typically shows a handful of spam mail messages containing attachments into which Windows malware has been hidden. This can be alarming but is actually harmless and, generally speaking, Windows malware can be identified because the name of it usually begins with "Win32" or "Win64". Even though this is harmless to Mac users, Bitdefender Virus Scanner will still remove it.
In addition to Bitdeferender Virus Scanner, we also recommend the occasional use ofMalwarebytes Antimalware, which focusses mostly on uncovering and removing adware - which is to say, hidden code within certain apps that aims to hijack your computing experience to show adverts on the desktop or in your web browser. Again, you can run Malwarebytes Antimalware infrequently to scan your system.
Enable two-step everywhere
Two-step authentication is a system whereby your login to services or websites requires more than just your username and password. It requires an additional numeric code. This is either sent to you as something like a text message or it's generated by a special app that runs on your mobile phone (there are many such apps but for the iPhone we recommend Authy).
Two-step verification is sometimes referred to by its more technical name of two-factor authentication, or TFA.
We've already discussed how to setup two-step verification for your Apple ID (look for the Securing Your Apple ID section), and we very, very strongly recommend you set it up because it presents an insurmountable brick wall to hackers trying to gain access to your account. In fact, stop reading this now and go and do it if you haven't already. We'll wait here until you've finished.
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