In this case simply open a terminal and run the following command from the directory where the actual BitDefender-Antivirus-Scanner-7.7-1-linux-i586.deb.run file is located:
$ sudo bash BitDefender-Antivirus-Scanner-7.7-1-linux-i586.deb.run
[sudo] password for username:
Scroll down License Agreement with SPACE BAR and type “accept” and ENTER to begin the installation. Depending on your installation you may also want to install graphical user interface:
Do you want to install BitDefender Antivirus Scanner GUI package ? (Y/n) y
After successful installation you will see message: