I think Ubuntu Linux itself doesn’t need an antivirus software.
But you can scan removable devices or Windows partitions in Ubuntu
system using an antivirus scanner. This tutorial is going to show you
how to install BitDefender Antivirus Scanner in Ubuntu from the official
deb repository.

First, hit Ctrl+Alt+T to launch a terminal window. Then run this command to add the BitDefender repository key to the list of apt trusted keys:

Run this command to add BitDefender repository:

Now, do update:

Once installed, you can launch it at next login.
First, hit Ctrl+Alt+T to launch a terminal window. Then run this command to add the BitDefender repository key to the list of apt trusted keys:
wget -O- -q http://download.bitdefender.com/repos
/deb/bd.key.asc | sudo apt-key add -
Run this command to add BitDefender repository:
sudo sh -c 'echo "deb http://download.bitdefender.com/
repos/deb/bitdefender non-free" >> /etc/apt/sources.list'
Now, do update:
sudo apt-get updateInstall BitDefender Antivirus Scanner:
sudo apt-get install bitdefender-scanner-gui
Once installed, you can launch it at next login.