There are many Antivirus software available in the market , among these AVG , Avasta ,Bitdefender ( for testing ) are absolutely free.
AVG Antivirus
Famous Antivirus for Windows PC's. It is totally free for Linux. Only problem we found is , no GUI , graphical user interface is absent , it run through terminal.
Download AVG for Linux ( 106 MB )
Download Deb file and double click on it
Enter password and follow the instructions
How to scan your computer using AVG Antivirus on Linux/Ubuntu
Avast Antivirus
Free edition . it's a good antivirus software, it has many features like GUI , fast scanning etc..
Size of the file is 27MB ,
Download Avast Antivirus
BitDefender Antivirus software
One of the best Antivirus software on Windows PC's. Now it is available on the Ubuntu/Linux.It is the only Antivirus software with a simple and beautiful GUI. We can automatically updates software in a single click.Installation is not difficult but it is not in the ordinary way. We need to install.deb.run file so we can't install using software center.
Register with Bitdefender and try Get a free trial
Then they will send you a Email with Serial number and Download link. After the installation update it.
Download AntiVirus software from here
BitDefender
Complete download .
Open Terminal
Navigate it to that folder /Choose the downloaded folder where you download antivirus software.
Example : cd Downloads
BitDefender installation step
type this command
sudo sh filename.deb.run
Example: sudo sh BitDefender-Antivirus-Scanner-7.6-4.linux-gcc4x.amd64.deb.run
When it complete type accept and enter
Enter Y to get GUI
Setup Bitdefender
Goto Ubuntu menu and type Bitdefender when installation complete