The Chemical and Biological Defense Command (or CBDC) is an organization in the Syphon Filter series. They are tasked in protecting against biological warfare from terrorists and are specialized in disposing of chemical weaponry, such as viral bombs. CBDC agents are authorized to use lethal force in dealing with terrorists, as seen during the Black Baton's attack on Georgia Street.
Appearance

They are commonly identified by their yellow full-body protective suit with black face-mask complete with a backpack. In Syphon Filter 2 however, their attire switches to that of a standard military dress such with green pants, a white t-shirt and dog-tags displayed hanging around their necks. Some agents can still be seen wearing these outfits during the investigation of the Pharcom Warehouses in Kazakhstan, with the facemask removed and hood pulled back.
Weaponry
The most common weapons used by CBDC agents are the M-16 and 9mm handgun.
Plot
Syphon Filter
Their first appearance in Syphon Filter involves their attempt to avoid the attack of the terrorists of Black Baton and defuse the bombs planted by them; with the help of Gabriel Logan, the CBDC defuse the bombs. After the missile incident they appear in the credits of the game.
Syphon Filter 2
In Syphon Filter 2 they appear in the first mission with Logan and are in a plane which is shot down. During the mission they are killed by Agency personnel until in the end all that's left are Ramirez and Chance. They are captured, but towards the game's end Logan frees Chance and gets him to release Ramirez. When Logan returned to Ramirez's cell, he finds him dead and in the final mission it's revealed he was killed by Chance, so Logan kills Jason Chance.
Syphon Filter 3
The CBDC do not appear in the story of Syphon Filter 3, but a CBDC agent is a playable character in the games multiplayer.