Prevents establishment of cellular antiviral state by blocking virus-induced phosphorylation and activation of interferon regulatory factors 3/IRF3 and 7/IRF7, transcription factors critical for the induction of interferons alpha and beta. This blockage is produced through the inhibition of host TBK1, by binding host TBK1 adapter proteins TBKBP1 and AZI2, thereby producing a strong inhibition of the phosphorylation and activation of IRF3 and IRF7. Acts also as an inhibitor of the cellular response to type I IFN by interacting with host STAT2. Mechanistically, exerts its inhibitory effect after host ISGF3 complex (composed of STAT1, STAT2 and IRF9) binding to the interferon stimulated response element (ISRE). Interacts with host TANK, TBKBP1 AND AZI2; these interactions prevent interferon production (PubMed:21931555). Interacts with host STAT2 (PubMed:27907166). Belongs to the orthopoxvirus C6 protein family.