Nuclease that is responsible for viral evasion of host cGAS-STING innate immunity (PubMed:30728498). Cleaves 2',3'-cGAMP which is produced by host cGAS following recognition of cytosolic DNA and blocks the subsequent 2',3'-cGAMP-mediated activation of TMEM173/STING, which normally spreads to adjacent cells and activates the interferon and NF-kappa-B immune responses (PubMed:30728498). 2',3'-cGAMP + H2O = Gp(2'-5')Ap(3') + H(+) Homodimer. The substrate binding site is formed by the N-terminus of a monomer and the C-terminus of the opposite monomer. Knockout induces a 40 fold decreased replication of the virus. Belongs to the poxin family.