Why does the Enterprise not have any physical access controls?

Question

A repeated plot device of TNG is sabotage and similar aboard the USS Enterprise.

Malicious agents infiltrate the Enterprises crew again and again by subterfuge, e.g. by posing as crew members, as shipwreck survivors in need of rescuing, as small children, in the guise of diplomats (or their attachees) etc.

These agents basically immediately gain free rein of the ship, and can inevitably be seen just minutes later accessing highly sensitive parts of the ship, such as engineering, med bay, captain's quarters, crew cabins, etc, etc. Now, of course this is a plot device, but, is there an in-universe explanation?

Why are there no proper physical access controls anywhere on the Enterprise? Why is seemingly everyone and their dog allowed to go everywhere? Have they lost the concept of keys, key cards, biometrics, etc.?

E.g. we can even see children wandering into areas where they "aren't allowed to go". Why aren't those areas simply behind closed, access-controlled doors?

We can see the (bridge) crew of the Enterprise cordon off entire sections via security gates or by shutting down turbolifts, bt that then closes them off for everyone. We hardly ever actually see anyone (be it crew or others) being prevented entry somewhere on Enterprise by a simple door lock. Why?

Answer 1

Security in Star Fleet seems to be more based on the honor system and less on physical restrictions or computer systems. Generally the people on board the ship are expected to know they aren't meant to go to certain places, this is why the turbolifts don't seem to have any issue taking children and re-animated investors to the bridge.

The only real security we see is when activating self-destruct. This requires multiple bridge officers to broadcast their security codes to each other before proceeding.

The Enterprise's security issues do not go unnoticed. Consider this exchange between Odo and Worf (shortly after Worf comes to live on DS9)

[Worf hauls a criminal into Odo's office]
Lt. Commander Worf : This p'tak just robbed my quarters.
Odo : [to deputy] Take him to a holding cell.
[the deputy takes the thief away]
Odo : I'll need a statement.
Lt. Commander Worf : And you will have one. But I want to know why such a security breach was allowed to occur in the first place.
Odo : Unfortunately, these things happen.
Lt. Commander Worf : They did not happen on the Enterprise.
Odo : Really? Now let me see.
[consults a PADD]
Odo : Stardate 46235.7: Ferengi privateers led by DaiMon Lurin boarded and seized control of the Enterprise using two salvaged Klingon Birds-of-Prey. Stardate 45349.1: Berlinghoff Rasmussen, a petty criminal impersonating a scientist, committed numerous acts of theft against the crew of the Enterprise. Shall I continue?
Lt. Commander Worf : That will not be necessary.
Odo : I know these incidents are the exception rather than the rule, but if security breaches like these could happen on the flagship of the Federation, imagine the difficulty of maintaining security at an open port such as DS9.
Lt. Commander Worf : I understand. It is just that I find it irritating.
Odo : So do I, but I'm afraid you're just going to have to get used to it. - IMDB

Particularly biting since Worf was chief of security on the Enterprise.

Answer 2

From TNG 1x26 The Neutral Zone, Picard here is objecting to the 20th century guest Ralph Offenhouse pestering him over the com system :

PICARD: Those comm. panels are for official ship business.
RALPH: If they are so important, why don't they need an executive key?
PICARD: Aboard a starship, that is not necessary. We are all capable of exercising self-discipline. Now, you will refrain from using them.

Critical information is generally secured, however. From Data's Day (TNG 4x11), here T'Pel is a Romulan spy posing as a Vulcan Ambassador and tries to extract classified information from Data :

T’PEL: Enter. (Data Enters.) You have a priority three clearance aboard the Enterprise?
DATA : That is correct, Ambassador.
T'PEL : I require information on this ship's defense and navigational systems. Access code: kappa-alpha-4-6-0-1-7-0-4.
DATA : The code is valid.
T'PEL : What is the field strength of the ship's deflector shields at maximum output?
DATA : May I ask the purpose of your request?
T’PEL: I require this information.
DATA: I have the same safeguards as the ship's computer. Therefore, I must report any inquiry regarding restricted information to the Captain. Your reaction suggests you do not wish the Captain to be informed of your inquiry.
T’PEL: I was not interested in the information. I was curious as to your security safeguards. They appear to be adequate. Cancel request. You may leave. (Data leaves)

So the concept of security keys and authentication does exist in the Star Trek Universe, it's just reserved for critical secrets and safety systems, while for non-critical systems it seems that officer and crew training and protocol are deemed generally sufficient.

This isn't to say that everyone who came on board the Enterprise had free reign of the ship. In The Wounded (TNG 4x12), three Cardassians come on board to hunt for the rogue Starfleet ship USS Phoenix commanded by Ben Maxwell and serious consideration is given to the degree of freedom they should have while onboard :

PICARD: There will be three Cardassians transporting aboard. Their Captain, Gul Macet and two of his aides. My intention is to be as open as possible with them, allow them to share in our search for the Phoenix.
WORF: Sir, it is necessary to assign them a security detail.
PICARD: They're our guests, Mister Worf. I don't want them to feel like prisoners.
RIKER: I tend to agree with Mister Worf, Captain. I think we should limit their access while they're on board. They don't need to have the run of the ship.
WORF: At least allow me to post guards in some of the sensitive areas of the ship.
PICARD: Very well, let's limit their access. But you instruct your people they are guests.
WORF: Aye, sir.

And the Enterprise does have dynamic physical access controls in the form of force fields which are ubiquitous in every corridor (and double as safety systems in the case of hull breach). These are always used in reaction to a direct threat, however, and not generally for access control. We see these used many times - during the hunt for Roga Danar, for example, or when trying to apprehend the legacy Klingons in Heart of Glory.

Beyond TNG, we do see other examples where physical access to a computer terminal still requires authorization to access secured information. The holographic Doctor, for example, in Message In A Bottle (VOY 4x14) found himself on the prototype vessel USS Prometheus, which happens to have been commandeered by Romulans. As such, the Doctor's security clearances are not recognized and his access to information is very limited, even though he has easy physical access to the computer systems themselves :

EMH: Computer, is there any way for me to gain access to the communication system to send a message to another ship?
COMPUTER: Negative. Communications access requires level four clearance or above.

and later

EMH: Computer, display the design schematic of this ship and list general specifications.
COMPUTER: USS Prometheus. Experimental prototype designed for deep space tactical assignments. Primary battle systems include regenerative shielding, ablative hull armour, multivector assault mode.
EMH: Multivector assault mode? Describe.
COMPUTER: Access to tactical data requires level four clearance.
EMH: What can you show me at my clearance level?!

As for locking doors, it is possible, but seems rarely used (for the self-discipline reasons noted above). From the same episode (VOY 4x14) we hear B'Elanna complaining about Seven of Nine having locked others out of astrometrics:

CHAKOTAY: Part of the problem is your attitude. You've never tried to accept Seven as part of the crew.
TORRES: And with good reason. Guess what she did this morning. She took an isolinear processor out of Engineering without asking, and when I went to Astrometrics to get it back she had locked the door, like that lab is her own private domain.
CHAKOTAY: What do you want me to do? Throw her in the brig for the rest of the trip home?

Answer 3

Security is a trade-off between the danger of letting the unauthorised in, and the danger of locking the authorised out.

In an emergency - something that happens with alarming frequency on the Enterprise - crew need rapid access to critical engineering systems. If there's a plasma fire, or overloaded phaser, or crashing shuttle, or imminent warp core breach, you don't want to be mucking about with swipe cards and passwords and keys to get into places. You don't want anything to impede crew efficiency and speed of action when rushing to repair battle damage in the middle of a fight.

In case of intruders, if they can bypass security to the point of being able to get on board, then they may very well have the technological capability to take over your security system too, and change all the passwords on you. You then find yourself locked in and unable to move. This is especially a risk when potentially dealing with aliens who might have vastly superior technology. So you never build any lock you cannot pick, no barrier you cannot get past yourself. You give the enemy no potential impregnable strongholds with which to counter your local advantage - you maintain a level playing field. You give yourself always maximum freedom of action, maximum capability, maximum options, and you rely on having superior training and local knowledge to win any conflicts.

And it is fairly apparent that the later Enterprises do have plenty of barriers that can be activated - force barriers at every corridor intersection, for example. But these security measures are all turned off by default. That gives an opponent less information, and less time to study them to find ways round them when they are turned on. If there are visible locks everywhere, a thief won't even bother to turn up until they're sure they've got a way past them. But if they turn up and see nothing but open corridors, they won't know what hidden inactive security there is that they might eventually have to bypass. You should always defeat the enemy with the minimum force you can get away with, so that they learn as little as possible about your full capabilities. You keep as many secrets as you can in reserve for future conflicts.

And it is also a part of the psychological philosophy of the Federation and Starfleet that people should generally be considered trustworthy and given maximum freedom, until they show cause not to. You learn a lot about a people's mentality by looking at how they live. Klingon and Orion ships have extremely heavy and intrusive security everywhere, because revolutions, crew mutinies, mistrust and internal fighting are a way of life, and society is violent, divided, and highly authoritarian. You know you cannot trust them within five minutes of walking onto one of their ships, for they don't even trust one another. If a new alien species walks onto a Federation ship, you want them to get a different impression. Aliens will hopefully be inclined to treat you like you treat them, so you treat them well. It's like them constantly making the point about Starfleet vessels being primarily for exploration, not war or defence. It's a statement about what sort of society the Federation really is.

Think of the ubiquitous visible security in 20th century Stalin's Soviet Union or Cold War East Germany, and contrast that with the openness and access in Western nations. Star Trek presents the society of the future as one that is even further down that road than 21st century Westerners are. This highly visible openness is part of the same utopian vision.

Answer 4

I've been on a few navy ships in my time and most of them didn't have locks on the doors except for private quarters as far as I can remember. There were locks on cabinets in some areas but you could walk from stem to stern and unless somebody saw you and physically stopped you nothing got in your way.

From memory there weren't even locks on the doors to the ammunition stores or to the areas where missile tubes were loaded from. I think that everything was done on the basis that only crew members were on board and that they all followed the rules.

Then again I might just be misremembering.

It's likely that the creators of the show would have used real life as a mirror, transposing the situations and experiences onboard a real ship into their futuristic setting.

We do know that from TNG onwards that they do have internal security systems because they use internal security forcefields to block the path of characters once they have been discovered to be up to no good. And that Private quarters have locked doors that require a security override in order to access them.

Answer 5

In addition to the other security policies people have noted, the holodeck repeatedly references the need for command level overrides in certain scenarios.

In the episode Decent, Data states that the holodeck safety systems can only be overridden with the authorisation of two senior officers.

DATA: Computer, reset Borg simulation to time index two point one. Increase Borg strength by twenty percent. Run programme.

(the Borg leaps up to throttle Data again. This time it is harder for Data to break free)

DATA: Stop it. Stop. Stop. Stop. Stop. Computer, reset simulation to time index two point one. Increase Borg strength by thirty percent.

COMPUTER: Unable to comply. A thirty percent increase would exceed safety limits.

DATA: Geordi, the computer will require the voice authorisations of two senior officers in order to disable the safety routine. Will you help me?

In the movie First Contact, Picard disables the safety systems in the holodeck to produce bullets that can actually kill. Presumably one captain equals two senior officers in this regard, or else maybe they changed the threshold offscreen at some point.

LILY: I think you got 'em. ...I don't get it. I thought you said this was all just a bunch of holograms. If it was just a hologram...

PICARD: I disengaged the safety protocols. Without them even a holographic bullet can kill.

Answer 6

I don't think people are allowed to wander anywhere they want. There's more than a few times we see that some areas are not very accessible.

The TNG episode Disaster has Picard having to give a tour of the ship to three children who won a science fair.

PATTERSON: Can we see the battle bridge and torpedo bay?
PICARD: No, I'm afraid not. But we will be visiting the hydroponics and astrophysics laboratories.

This implies the children know of these locations, but, due to their strategic importance to the ship, they cannot access them. We see a similar hint in the first episode Encounter at Farpoint

(The turbolift doors open, and Wesley is standing there)
PICARD: Children are not allowed on the Bridge.
(Crusher appears from where she was hiding)
CRUSHER: Permission to report to the captain
PICARD: Doctor Crusher.
CRUSHER: Captain. Sir, my son is not on the Bridge. He merely accompanied me on the turbolift.

The implies the only reason the turbolift would take them to the bridge is because an officer requested it. We never see children simply show up on the bridge either, despite seeing them roam the corridors freely.

As for door locks, they absolutely existed. Rather than throwing people in the Brig, you could confine them to quarters. In The Wounded we see

(Worf hauls Telle onto the Bridge)
TELLE: I will protest this, Klingon!
PICARD: Lieutenant?
WORF: He was found at a computer station on deck thirty five, attempting to access information on our weapon systems.
TELLE: A lie, Gul Macet. I was studying the terminal interface systems. They're more efficient than ours. I have no idea what was in the files.
MACET: What business did you have going near one of their computers?
TELLE: But, Gul Macet, I meant nothing. There was no harm done.
MACET: Go to your quarters. You are confined there for the duration of this expedition.
TELLE: As you wish, sir.

And later

Captain's log, supplemental. Captain Maxwell has turned his ship over to his First Officer and transported aboard the Enterprise. I have confined him to quarters for the return voyage

Answer 7

Access control is a defence-favouring technology. Offence is, as far as battle tactics are concerned, about getting somewhere the enemy doesn't want you to be. Defence is about stopping the enemy before he gets somewhere you don't want him to be. The eras where the available military technology makes it easy to kill someone are biased in favour of defence, while those where killing someone is difficult are biased in favour of the offence.

Stories of battlefield exploits from offence-biased eras are more entertaining than those from defence-biased ones. A tale kids infiltrating a castle is more appealing than one of teenagers sitting in a muddy trench waiting to be blown up by a shell.

Access control poses a problem for story-writers because just makes the whole world so much more boring. I remember watching the French series Lupin, whose titular character is given a universal RFID card that hacks through any access control system to eliminate access control from the universe by deus ex machina.