Prevents the establishment of cellular antiviral state by blocking the interferon-alpha/beta (IFN-alpha/beta) and IFN-gamma signaling pathways. Blocks the IFN-induced nuclear accumulation of host phosphorylated STAT1, by interacting with the STAT1-binding region of host importin alpha-1/KPNA1 protein, thereby inhibiting the latter. Without the activity of this protein, activated STAT1 would not enter the nucleus and be unable to activate IFN-induced genes. Plays a role in assembly of viral nucleocapsid and virion budding. May act as a minor matrix protein that plays a role in assembly of viral nucleocapsid and virion budding. Interacts with host importins KPNA1, KPNA5 and KPNA6. Interacts with host STAT1. In virion, localizes on the intravirional side of the membrane. In the host cell, it is found associated with virus-induced membrane proliferation foci and to the plasma membrane where budding takes place (By similarity). Belongs to the filoviridae membrane-associated protein VP24 family.