How do the interferons protect the body against viruses?

Toxic to viruses. Interferons are directly toxic to viruses; i cannot comment on the exact mechanism, however.
Interferons. Interferons (ifns) are proteins made and released by host cells in response to the presence of pathogens such as viruses, bacteria, parasites or tumor cells. They allow for communication between cells to trigger the protective defenses of the immune system that eradicate pathogens or tumors.