The Sentinels (and other superheroes/villains) usually maintain secret identities - usually their real identities when out of costume, or for blending in with the local population. There are three generalised status levels:
Status: Public
The character's real identity is no secret and the character makes little to no attempt to hide it. It may be known by everyone, or it may simply be known by a few people, but the character does not actively try to hide it. For all intensive purposes, the character has no secret identity. An example is Rocky, who cannot hide his mutations and was a well-known local actor for a while before joining the Sentinels. On the other end of the scale is Dragoneye who's identity is well known to the Sentinels, A.R.G.U.S. and the Jadetown criminal underworld, but most of the Jadetown population do not know mostly out of ignorance (why humanize your gods?).
Player Metaknowledge: Any Codex entries for these characters can be assumed to be public knowledge with a little effort or the right connections, so players can assume their characters know this information if they wish. There may be exceptions, e.g. Sophie Anderson's identity is secret, but her Bonnet Blanc and early hacking days are secret (in fact, it is difficult to find any information about her anywhere, so most of what players would know about her would be based on what they ask her).
Status: Confided
The character's real identity is an "open secret" - that is to say that the general public does not know the secret identity of the character (so hopefully, neither do the villains), members of the Sentinels are privy to the character;s real identity. This is the default status for most of the Sentinels, who help protect each other and keep each other's confidence. An example is Wyrmhole who is known by all the Sentinels to be Stephanie Jones, but the general public only know her as Wyrmhole.
In the case of villains, this means that either the Police, A.R.G.U.S. or The Sentinels (Emerald City Knights) may be aware of the characters real identity, but the general public is not. An example of this is Zhar-Ptitsa (Firebird) who is publically known as Zhar-Ptitsa (or Firebird by those who do not speak Russian) but her real identity of Nadezhda Diordiychuk is known the Sentinels
Player Metaknowledge: Codex entries are for player OOC information but their characters may not know some or all of the information presented. Players should check with the GM about any knowledge they want their characters to know, or else the GM may prevent this metaknowledge being used. E.g. reading the Codex entry for Princess will reveal her secret identity and background, but none of the players would know any of this in game.
Status: Secret
Similar to Confided but, for reasons of their own, this character keeps their secret identity secret even to other Sentinels. This is usually done by new (or paranoid) characters who have trust issues, or want to keep their "work" and "private" lives separate. Despite this, their secret identity is known by at least some other (though not necessarily a sentinel). An example of this is Princess, who's real identity is not known by most of the Sentinels, but at least one (Wyrmhole) knows her true identity. Likewise, most of the original Sentinels know Ultramarine's secret identity, but Ultramarine is never around the newer Sentinels without the Ultramarine Power Suit and the helmet on, only removing the helmet when with Sentinels Ultramarine trusts.
In the case of villains, this signifies that neither the police, A.R.G.U.S. or the Sentinels know their real identities yet, but the likelihood is that someone, somewhere, does. An example is the rogue vigilante Revenant. The Sentinels have clashed with him on occasion, but have made no progress in learning his true identity, although it is presumed that some members of his vigilante group might know (but are not talking).
Player Metaknowledge: Codex entries for these characters will usually be written with what someone has uncovered, either a player or an npc, often with the expectation that the players can, through good roleplaying, learn more about these characters (bringing them to "Confided" levels). As things are uncovered (usually in game) the The player characters are assumed to not know anything other than what the GM informs them they may know (players can ask) or they have experienced themselves in game.
Status: Unknown
The character's true identity and/or origins are unknown to pretty much everyone. The character is a mystery and all that is known about the character is what has been witnessed first-hand. This does not apply to any of the Sentinels, as there is a general policy that Sophie Anderson must register in CAIn, every Sentinel's identity (normally a DNA sample entry kept locked inside CAIn and inaccessible by Sentinels). This is to prevent enemies of the Sentinel's infiltrating the group simply by wearing a mask and refusing to reveal their identity. Whilst the Sentinels will gladly ally themselves with masked heroes that conceal their identities from them, no hero that refuses this requirement will be allowed membership.
Player Metaknowledge: Codex entries for these characters will usually be written "player safe" with only what they know - often with the expectation that the players can, through good roleplaying, learn more about these characters (bringing them to "Confided" levels). Some characters (likely those who's past/identity will never be revealed, usually due to magic or supernatural causes) may have their bios written, but the player characters do not know anything other than what little the GM informs them they may know (players can ask) or they have experienced themselves in game.