Hopper virus infects .VBS files and Word documents, as well as HTML files. VBS/Hopper.A infects other .VBS files by prepending it's code to the original file.
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.
Some variants of this virus family also infect HTA and HTT files. Some of them lower the security settings of IE's zones. To ensure that the virus works on all platforms, when infecting VBS and DOC files, it comments out the HTML-specific part of itself. It infects documents when closes them.
Some variants of VBS/Hopper are able to infect Excel files as well.