PHP/Pirus is the first virus written with PHP. PHP is a server side scripting language for web servers.
Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.
More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for more information.
When PHP/Pirus.A is executed, it will search for files with ".php" and ".htm" from the current directory. If such files are found, it will append a small code that will execute the virus from a separate file. The name of the file is "pirus.php".