Interferon-induced antiviral exoribonuclease that acts mainly on single-stranded RNA (PubMed:11401564, PubMed:12594219, PubMed:16033969). Exhibits antiviral activity against RNA viruses including hepatitis C virus (HCV), hepatitis A virus (HAV) and yellow fever virus (YFV) (PubMed:16514659, PubMed:21036379). Inhibition of several viruses such as chikungunya virus (CHIKV) does not involve the degradation of viral RNAs, but rather the inhibition of translation of viral proteins (By similarity). Exerts a translational control over a large panel of non-self RNA substrates while sparing endogenous transcripts. This activity correlates with the protein's ability to localize in cytoplasmic processing bodies (PubMed:31600344). May also act as master regulator of over hundred interferon stimulated genes leading to viral genome translation inhibition (By similarity). May play additional roles in the maturation of snRNAs and rRNAs, and in ribosome biogenesis (PubMed:16514659). {ECO:0000250|UniProtKB:Q9JL16, ECO:0000269|PubMed:11401564, ECO:0000269|PubMed:12594219, ECO:0000269|PubMed:16033969, ECO:0000269|PubMed:16514659, ECO:0000269|PubMed:21036379, ECO:0000269|PubMed:31600344}. This is the function of Ensembl gene identifier ENSG00000172183 (ISG20, interferon stimulated exonuclease gene 20).