| "M.O.S. (Mystery Operation Squad) is a special operative squad dedicated to investigation on paranormal activity. The nationalities and purpose of the members of the squad are unknown even between mercenaries."|
- in-game description
SIA(Secret Intelligence Agency) is a male character featured in CrossFire.
- CF China
- CF Vietnam
- CF North America
- CF Philippines
- CF Indonesia
- CF Russia
- CF Brazil
- CF Europe
- CF Korea
- SIA is the first male character to feature fingerless gloves for both BL and GR model.
- When MOS (Mystery Operation Squad), SIA's CF PH name, was released in the CF PH, the character was not fully-detailed. Its long hair and ponytail for BL and its spiky hair for GR was not present so it only shows the brushed up, flat hair of the character which is being used when the character has a head equipment/gear. The appearance was later changed in a certain update in CF PH.
- In CF PH, SIA has an opening price of 150 eCoin. Its price later became 200 eCoin.
- CF Vietnam's description for SIA states that he has "never known defeat, nor anyone survived to tell the tale". Whether this is true or not strictly depends on players using him, although it's mostly impossible to never lose (unless that player only farm ZM/MM/HM/HMX).
- In CF Japan, crates with this character has skin alongside his glasses.
- S.I.A's GR model is often potrayed as GR Leader in many of CrossFire's CGI movies.