HLL is a family name - all parasitic viruses written in High Level Languages, such as Pascal, C, C++ or Basic, have been grouped under this name.
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.
There are several members, including the following viruses: HLL.3680, HLL.Pascal.3966, HLL.5150, HLL.5602.A, HLL.5602.B, HLL.Bobas, HLL.5938, HLL.Rna.7296, HLL.Rna.7408, HLL.Pascal.7808, HLL.Cookie.7360, HLL.Cookie.7392, HLL.Halloween, HLL.Antiline.
Members of the HLL family are rarely seen in the wild, but the chance of a false alarm is bigger than with viruses written in assembly language - this is because it is more difficult to find a distinct search string for these viruses.
See: HLLO, HLLC.