Interferon-stimulated protein that plays an important role in innate immune response against a wide variety of viruses (PubMed:31142663). Inhibits flavivirus replication by preventing the formation of virus-induced endoplasmic reticulum membrane invaginations, which are double-membrane vesicles that flaviviruses use for their replication (PubMed:30224801). Has an antiviral activity towards hepatitis C virus/HCV by inhibiting the EGFR signaling pathway, whose activation is required for entry of the virus into cells (PubMed:25757571). Within the nucleus, restricts hepatitis B virus/HBV promoter activity leading to substantial reduction of viral replication and gene expression (PubMed:33868257). Plays a role in apoptosis, negatively regulating the intrinsinc apoptotic signaling pathway and TNFSF10-induced apoptosis (PubMed:15685448, PubMed:17823654, PubMed:26244642). However, it has also been shown to have a pro- apoptotic activity (PubMed:27673746). Modulates innate immune response mediated by RIGI by preventing its activation (PubMed:36793726). {ECO:0000269|PubMed:15685448, ECO:0000269|PubMed:17823654, ECO:0000269|PubMed:25757571, ECO:0000269|PubMed:26244642, ECO:0000269|PubMed:27673746, ECO:0000269|PubMed:30224801, ECO:0000269|PubMed:31142663, ECO:0000269|PubMed:33868257, ECO:0000269|PubMed:36793726}. This is the function of IFI6 (interferon alpha inducible protein 6, Ensembl gene identifier ENSG00000126709).