You don't need any of these in Linux (they won't work anyway). You don't generally defrag in Linux anyway - the way the IO schedulers and Linux filesystems work, defragmentation is far less of a problem and is, in most scenarios, completely irrelevant. That's not to say that it doesn't happen (it does), but for various reasons (I don't know anything of the internal workings of NTFS or Windows IO scheduling so I can't comment on them) it's less common under Linux and the effects of it are less pronounced. There are tools for defragging Linux filesystems (ext4 supports online defrag though I don't know it tends to come enabled by default), but the general consensus is that its useless and even risky. In any event, if you want to defrag Linux partitions, use tools designed for those filesystems (I'm pretty sure auslogics only handles Windows filesystems), you can usually get them from your distro's repositories.
There aren't really any "out there", it is true that proof-of-concept and such viruses have been created but at least I've never heard none of them are able to spread themselves and they've never escaped lab setting.
It's only for Windows malware. Apparently it's popular among people running mail servers, though I suppose it's handy to have if you want to make sure that no infected portable media ever gets to a Windows system.
