The Siren strain was first accounted in October 1950, when the Chimera diverted the Thames River into Central Command in London, drowning 14,000 British soldiers. In which according to a survivor's accounts, many of the soldiers that survived from the flooding were torn apart and eaten by Sirens before some that didn't began to willingly to go into the flooded water to their deaths as if they were in a trance, hence the Siren's name.
Unlike the Furies that appear in Resistance 2, Sirens have the ability to create telekinetic blasts to attack their enemies, and are able to be killed by gunfire, however can only be killed underwater with energy weapons. Sirens also appear to be mutated exclusively from female humans.
- Because Sirens can only be found underwater and in water-like substances, it is important to know that only energy weapons will work against them. Only the Auger WS, Longbow 1S-1K, the BM001 and BM003 Razors are capable of functioning underwater and dealing damage to them.
- The Advanced Auger-FS is also extremely useful against Sirens, as its shield is indestructible and will reflect projectiles back at the enemy who fires them.
- The Siren is named after the dangerous bird-women who sang enchanted songs to sailors which lured them to shipwreck on rocky coasts.