Avira is a German-produced antivirus package which has a Unix/Linux version in addition to those for Windows.
This is, largely, aimed at running the package as a daemon carrying out tasks such as scanning a mail spool directory, or shared disks/directories that more vulnerable systems may access, to catch malware before it is passed on to Windows machines.
The PDF manual for the Unix/Linux version is aimed at a 'junior sysadmin' level, and it is recommended that you read through this first, in its entirety. Anything beyond a "vanilla" configuration which scans /home will require the editing of config files.
Once you have downloaded the gzipped installation file, you have to unpack and install it. This is achieved in a terminal window as follows:
$ cd /tmp $ gunzip ~/Downloads/antivir_workstation-pers.tar.gz $ tar -x -f ~/Downloads/antivir_workstation-pers.tar
Note that the unpacking commands differ from that specified in the Avira documentation!
You will have created a directory containing the full Avira package in /tmp now, in running through the process I've ended up with antivir-workstation-pers-188.8.131.52-0.
The license key is, slightly confusingly, labelled as for Windows. However, it is perfectly usable for Linux too. Simply download or copy it into the newly created directory.
$ cp ~/Downloads/hbedv.key ./
Regrettably, the dazuko file system kernel module is no longer maintained, which means you cannot have genuine realtime scanning.
Building the package is straightforward:
$ cd antivir-workstation-pers-184.108.40.206-0 $ sudo ./install
And, follow the prompts.