Security Systems

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One thing that can be difficult to secure is communications. A transmission can be overhead by anyone with a receiver tuned to the proper band, making communications vulnerable. A number of technological solutions have developed to keep communications private and prevent eavesdropping, but for every technique of covert communication, there is a way around it.


The simplest means of keeping a communication secret is by using some sort of pre-agreed code essentially an artificial language that conceals the true information of the message. Starfleet encodes high-priority messages and has coded communications channels for (relatively) secure communications through subspace. Species like the Ferengi routinely encode all their communications. In the age of isolinear computer processors, codes can be very complex. Fortunately, with the help of the same computers (and universal translation software) it is still possible to break most codes, given time.

Code breaking uses the Espionage (Encoding) skill. It is an Extended Test, with a turn length of 15 minutes. The Difficulty of the test and the total Test Result required are based on the complexity of the code, and the tools available at the character's disposal. Fairly simple codes are Routine and require a total of around 10, while complex codes a Challenging or higher, and require a total of 30 or more. Ferengi codes are Nearly Impossible to break. Several characters can work together to break a code, making it a Combined Test (ST:TNG, p. 121).


Encryption is a complex mathematical algorithm that scrambles the information content of a transmission. The receiver can reconstruct the message using a special mathematical sequence called an encryption key. Encryption is handled by computers, which are capable of performing the massive calculations required. Complex encryption sequences are very difficult to break, requiring considerable time and computing power. Decrypting a message is an Extended Test of the Espionage (Encoding) skill or Physical Sciences (Mathematics). The turn length is 30 minutes; breaking encryption takes considerable time. The Difficulty and total Test Result required are based on the complexity of the encryption sequence. Most encryption is a Difficulty of at least Challenging, and a Total Result of 30 or more.


A common means of covert communication is "piggybacking" a transmission within another, innocuous signal to prevent it from being noticed. This requires a carrier signal of the proper strength (like a subspace transmission) going in approximately the same direction that the message must travel, and detectable by the intended recipient. Successfully piggybacking a message requires a Shipboard Systems or Personal Equipment skill test using the Communications specialization. The Difficulty is based on the conditions, but should be at least Moderate, Challenging is more common.

One simple means of piggybacking a message is by sending an extremely simple signal, like Morse code or another repeating pattern. This can often be disguised as background noise or static. It's a Routine or Moderate Difficulty to send, but it's more difficult for the receiver to notice it unless they're expecting to get such a message.

Filtering Communications

With 24th century computer technology, it's a simple matter to modify the sounds and images transmitted in communications. A Shipboard Systems (Communications) Skill Test allows a character to modify a communication, altering its visual and audio components to present whatever image the character wishes. The Difficult of the test is based on the complexity of the change desired. Making the captain look like a Klingon, standing on a Klingon bridge, for example, might be Moderate, while making the captain appear as a Tholian or a Sheliak, speaking in their native language, is Challenging at least.

A communications filter changes the way the receiver sees and hears communications sent from the ship. For example, a filter might make the crew look like Cardassians, standing on the bridge of a Cardassian ship. This is a useful supplement to the other forms of deception. If a patrol ship's long range sensors tell them they are tracking a Cardassian freighter, and their communication with the ship shows a Cardassian crew on board, they're not likely to suspect that the vessel is really a Starfleet Nebula-class starship.

Computer Systems

The center of nearly every security system in the 24th century is a computer. Control the computer, and you control the security system. The computer is the "brain" of a starship or installation, making it one of the parts most vulnerable to subversion and attack. Since the computer controls many functions automatically, completely outside the control of its crew, damage or sabotage of a ship's computer can sometimes leave it helpless.

Starship computers communicate with the outside world in a variety of different ways. They use the ship's external sensors to gather information for navigation, to avoid hazards to the ship and crew, and to provide the crew with useful information about their surroundings. They use internal sensors to monitor the locations of crewmembers, route communications, maintain environmental conditions, and dozens of other functions. Communications (both internal and external) are routed through the ship's computer, and the computer is in regular contact with outside sources of information like time-base beacons, surveillance satellites, probes, and similar objects. Computers on board stations, or planetside, function in much the same way.

A character can attempt to use the Computer (Data Alteration/Hacking) skill to gain unauthorized access to a computer. Computer systems contain multiple levels of security to prevent this sort of unauthorized access, making it difficult under most circumstances. This is an Extended Test (ST:TNG, p. 120) with a Turn Length of 5 seconds (or one combat round). The total cumulative Test Result required is up the Narrator, but should be at least 30, more for foreign or alien computer systems. The difficulty is based on the familiarity of the computer system: Moderate for very familiar systems (a Starfleet officer accessing a Starfleet computer), Challenging for somewhat familiar systems (a Starfleet officer accessing a Klingon computer), Difficult or higher for unfamiliar or alien systems.

The enemy can roll a Computer or Starship Systems (Sensors) Test against the infiltrator's Test Result each turn to determine if the intrusion attempt is detected. A dramatic failure on the infiltrator's part automatically alerts the enemy to the intrusion attempt. Once the enemy is alerted, the Computer Skill Test becomes an Opposed Test. A character on the enemy ship can make a Computer (Data Alteration or Programming) Skill Test each turn. Subtract the enemy's Test Result from the character's cumulative total each turn, representing the enemy wearing away at the infiltrator's success by using security measures to block him.

Example: Ensign Roberts is trying to gain access to the computer of a Federation ship under the control of hijackers to gain his ship a tactical advantage. The Narrator sets the total Test Result required at 30 (since Ensign Roberts is quite familiar with Starfleet computer systems). Roberts makes his Computer Skill Test, scoring a Test Result of 8 on the first turn. The Narrator makes a test for the enemy. The hijacker at the bridge tactical station hasn't noticed the intrusion, so far, so good.

Roberts makes his second test, while the Captain is talking to the leader of the hijackers, stalling for time. This time he gets a Test Result of 6, he's almost halfway there, when the hijackers notice him. They break off communications and open fire. "Keep at it, Ensign!" the captain says. Roberts makes his third test. This time, the hijackers are attempting to block him. Roberts gets a Test Result of 6 again. The Narrator rolls a total for the hijackers, getting a 4. Fortunately, they're not too computer savvy. Still, Roberts has a net gain of only 2 points on his cumulative total this turn, bringing it up to 16. It's in doubt whether or not he'll be able to gain access to the other ship's computer in time to do any good.

Passwords and Prefix Codes

The above rules assume the character does not have authorized access to the computer system. In some cases, however, the character may have access, in which case only a Routine Computer (Data Alteration or Programming) Skill Test is required to carry out the character's commands. This was the case in the Next Generation episode "Peak Performance," where Lt. Worf accessed the Enterprise's computer from the U.S.S. Hathaway and fed it false sensor data. When Data changed the security access codes, he blocked Worf's access.

Part of an operation to penetrate a location's security may consist of getting the proper access codes for the location's computer, circumventing its security measures. This is not as simple a matter as finding out a password or a sequence of numbers. Computers in the 24th century are quite intelligent, and generally have voice-recognition capabilities as well, so a password or code may need to be delivered by a particular voice as well. Voice synthesizers may be able to get around this problem. If the computer requires an additional verification like a DNA scan further counter-measures are required.

Starfleet gives each starship its own prefix code, providing outside access to the ship's computer to other Starfleet personnel. In the event of an emergency, or a takeover of the ship, another Starfleet vessel can use the prefix code to override the ship's computer system and take command of its key functions. In effect, a character on the other ship can operate the ship's computer as if it were an extension of his own ship's computer. Clever and knowledgeable hijackers will change a starship's prefix code as soon as possible to prevent other Starfleet vessels from simply overriding their command systems and, say, shutting down their shields or warp drive.

Command Codes

Codes can also be used to limit computer access to certain authorized individuals or locations. This is routinely done on board Starfleet vessels and installations; computer users must give an authorization code (by voice, so their voiceprint can also be scanned) in order to access certain restricted information and functions. For example, only the captain and the first officer of a starship can access the ship's auto-destruct system, and only in tandem. The more limited the system's access, the harder it is to overcome its security protocols.

Authorized characters can also oftentimes change the available access. For example, the captain of a Starfleet ship has the authority to localize command functions, preventing the ship's computer from accepting commands from any locations other than the one's specified. The captain can also lock out any or all of the computer's functions and place a code that unlocks them into the system. Until an authorized person inputs the code, those computer functions are no longer available.

Finally, as an emergency measure, the ranking command officer can lock out all of a starship or starbase's command functions, preventing anyone from accessing the computer until those functions are restored. This is done to prevent an enemy for seizing control of a boarded ship, allowing the crew the opportunity to take counter-measures.

Deflector Shields

A ship's deflector shields are its prime means of defense against attack. Although shields can be overcome with sufficiently powerful force, enemies may choose to rely on clever tactics to penetrate an enemy's deflector shields, especially if they lack weapons sufficiently powerful to penetrate them otherwise.

Shield Modulation

One tactic for penetrating deflector shields is to learn the exact modulation, frequency, and nutation of the shield. With this information and a Routine (3) Shipboard Systems (Tactical or Weapons Systems) Test, it is possible to adjust an energy-based weapon, such as a phaser, disruptor, or photon torpedo, to penetrate the shields as if there weren't even there. Such an adjusted weapon ignores the effects of the target's shields altogether. Given the power of most starship weapons in the 24th century, such an attack can be devastating.

The key to pulling it off is getting the exact shield data, which cannot be obtained by sensor scans, it must come directly from the opposing ship's computer system in order to be effective. This means the attacker must either infiltrate the other ship's computer to obtain the data (see Computer Systems, above) or they must have an agent on board the opposing ship able to transmit the data to them. Klingon renegades Lursa and B'Etor used this tactic against the Enterprise-D, resulting in the destruction of the ship's stardrive section (and the deaths of the Klingon sisters, as well).

This tactic is best used as a sneak-attack. Once the target realizes what is happening, all they need to do is rotate the shield's modulation, frequency, and nutation to block the enhanced weapons. The attacker needs to obtain the modulation data again and re-tune their weapons to the new settings.

Shield Override

Infiltration of the enemy ship's computer system can allow an attacker to override and shut down the enemy's shields. This is usually quite difficult under normal circumstances, but it's possible if the attacker has the enemy ship's prefix code, giving them easy access to the computer and command systems. Using the prefix code to shut down the other ship's shields is standard Starfleet procedure when confronting a Starfleet vessel that's been hijacked or is otherwise under unauthorized control.


Characters can use plain and simple trickery to get an opponent to lower their shields voluntarily. The most common tactic relies on the fact that shields inhibit transporter function. By choosing to "play dead," a ship can wait until an enemy closes to transporter range, then lowers their shield to beam over boarding parties. At that moment, the enemy ship is vulnerable to attack.

The difficult part of this tactic is it requires an enemy likely to board the ship rather than simply destroy it, such a raiders, or an opposing military force. It also requires the ship to lower its own shields and shut down enough systems to appear helpless. Make an Opposed Test of the Starship Tactics Skills of the characters involved (either the captains or tactical officers of the ships). If the ambushing ship is successful, their opponents are caught off guard. Once the enemy ship is able to act, they can raise their shields again with a Routine (3) Shipboard Systems (Shields) Test.

Characters may also be able to get an enemy to lower their shields using other tricks. The Narrator should judge their chance of success, based on an appropriate Skill Test.

Transporting Through Shields

Under normal circumstances, deflector shields block the operation of transporters, neutralizing any tactical advantage they might offer. However, a character may be able to find a weakness in the shields and transport through them. For example, the shields have to cycle in order to allow the ship's sensors to pick up information. The "window" created by the cycle is extremely small, only a fraction of a second, but enough for a skilled operator to take advantage of it. This requires a Challenging Shipboard Systems (Transporter) Skill Test, and is usually only possible when the shields of the transporting ship are down, making it a dangerous maneuver at best in the midst of combat.


Locks keep things that open closed-from doors to boxes. A lock can be a simple mechanical affair (easy to overcome with the right tools) or a more sophisticated electronic lock. Electronic locks usually have additional security features built into them, such as identifying their owner by fingerprints, retinal print, voice, DNA scan, galvanic skin response, or similar criteria. Locks can be overcome using proper tools and the Security (Security Systems) skill. Generally, opening a lock is an Extended Test with a turn interval of 5 seconds (1 round) and a Difficulty and required Test Result Total based on the sophistication of the locking mechanism and the availability of tools.

Lock Difficulty Table

Type of Lock Difficulty Test Result Total Required
Simple mechanical Routine 10
Complex mechanical Moderate 15
Simple electronic Moderate 18
Complex electronic Challenging 25
Sophisticated electronic Challenging 30 or more
Limited tools +2 +5
No proper tools +4 +10

Security Procedures

Starfleet uses a large number of security procedures and protocols to safeguard the lives of its personnel, and to prevent valuable Starfleet resources from falling into the wrong hands. Starfleet's complete security regulations take up a book many times the size of this one, covering everything from proper handling of prisoners to emergency situations.

It would be impossible to cover every aspect of security operations in complete detail. This section provides an overview of the most basic and vital security operations, allowing the Narrator and the players to extrapolate from it and information from the Star Trek shows, and other products from Last Unicorn Games.

Guarding Vital Areas

One of the primary duties of the Security department on board a starship or starbase is safeguarding vital areas that may be vulnerable to theft or sabotage, or that might draw intruders. Such areas include the bridge, main engineering, the central computer core, cargo bays containing valuable goods, the shuttlebays, and the brig. When the ship or station is not on alert, guards are routinely posted at security stations on the decks located near these vital areas, able to monitor the security scanners and respond quickly if there is a need.

For a yellow alert, security personnel are placed on guard at vital points throughout the ship. They may be given special orders regarding access to those facilities (such as allowing no one but the Captain and First Officer access). The security guards allow access to authorized crewmembers unless ordered otherwise. The Captain, First Officer, or Security Chief can also give certain crewmembers access privileges, as needed.

Under red alert, security guards are posted on all decks, as well as vital areas of the ship. If an intruder alert is sounded, security personnel guard all turbolifts and airlocks, and begin sweeping the ship for signs of intruders. Information is relayed back to the main computer and the Security Chief.

Standard procedure calls for at least one security guard on duty in the transporter room when unknown or potentially dangerous individuals transport on board. The transporter chief can hold such individuals in stasis in the pattern buffer if necessary to await the arrival of security, and transporter scanners automatically detect any dangerous weapons or other devices, and can render them inoperative before the subject rematerializes, making security's job easier.

Guarding the Captain

One of the prime duties of Security is safeguarding the commanding officer of a starship or station. The captain is considered a vital element of the ship, and treated accordingly. The captain should have a security escort at all times in red alert situations, and when beaming down into any situation that might become dangerous. The Security Chief and/or Operations Officer helps to safeguard the captain while on the bridge, but additional security personnel should be present if trouble is expected.

Part of safeguarding the captain involves performing security sweeps of areas before the captain enters or beams into them. Security personnel check for any potential hazards and ensure they are within reasonable limits before the captain arrives. The captain can, of course, override standard security procedures in these matters, but it is not recommended.

Away Team Procedures

Security personnel form a vital part of Away Team Missions and every away team is well-advised to have at least one security officer, more if the Away Mission is expected to encounter trouble (particularly armed resistance). In some cases, away teams may be made up entirely of Security (and Command) personnel.

While on an Away Mission, the duties of the Security personnel include: 1) Remaining alert for any signs of danger to the crew or mission; 2) Safeguarding the lives of all away team members, particularly senior officers; 3) Gathering tactical and strategic information regarding any possible threats; and 4) Taking necessary action to ensure the first three priorities, including the use of force, but only as a last resort.

While all Starfleet personnel on Away Missions are expected to remain alert, it is the security officer's duty to look out for potential threats to the Away Team. This includes the use of tricorder scans for hazards (both natural and artificial) and "reading" the reactions of any life-forms the crew may encounter. The security officer should make recommendations to the commanding officer of the Away Team with regards to appropriate security precautions.

It is important to note that Starfleet security officers are expected to take a defensive posture with regard to possible threats. Stunning (much less injuring) native life-forms "simply because they might pose a threat" is against Starfleet regulations. A strategic withdrawal is normally the most prudent response in a dangerous situation, followed by neutralizing the danger as quickly as possible, if a withdrawal is not an option.

Red Shirt Syndrome

Security "extras" in the Star Trek television shows get regularly phasered, stabbed, blow up, disintegrated, frozen solid, and eaten by alien life-forms with such regularity that it's become something of a joke among Star Trek fans. Called "Red Shirt Syndrome" (for the red shirts security personnel wore on the original series), it leads players to believe that any security NPC who accompanies them is surely a dead man.

In some cases, you can use this to your advantage, killing off non-player security characters for the same reasons Star Trek writers have: mainly to show just how dangerous a particular threat is, or to show off its unique (and probably unpleasant) means of killing people. Red-shirts also make good characters to get turned into sludge-rats (or styrofoam polygons) by omnipotent alien entities.

You can also play players' red-shirt expectations against them. For example, a non-player character who's not a security officer might suffer an unfortunate fate. Science officers are a good second choice, since they're usually investigating phenomena that can turn deadly without even a moment's warning. In certain situations, you can also throw players for a loop by having the malevolent alien choose one of their characters to kill first! Things should ideally turn out to be an illusion of some sort (or something else should be able to bring the character back to life). But putting the players in the role of the "red shirts" sometimes can lend a feeling of tension and fear to the game, and make the players a bit less likely to treat NPC security officers like cannon fodder.


There are occasions when a Starfleet crew may find itself with prisoners: criminals they have apprehended, captured attackers, or even unknown aliens. In general, Starfleet crews are authorized to keep such individuals imprisoned until they can be turned over to the proper authorities, either of the planet or civilization that has jurisdiction, or to Federation authorities at a Starbase.

Each starship or station is generally equipped with a brig to hold prisoners. The brig consists of one or more cells equipped with force fields and a security station. On board larger ships and space stations brigs are capable of holding a number of prisoners. Smaller ships may only be able to hold a handful, while the smallest ships may not have a brig at all. Crews may resort to using guest- or crew-quarters as makeshift cells by locking the door and posting guards (perhaps even reinforcing the door with a force field). Most brigs use force fields to prevent any chance of the prisoner escaping via transporter.

A starship crew is expected to turn any prisoners over to the proper authorities as soon as reasonably possible. The captain, of course, is the judge of what is "reasonable" in these situations. If the ship is already engaged in a mission, the prisoners may be held until that mission is complete and the ship has an opportunity to deal with them. More delicate political and diplomatic situations may require the crew to deal with their prisoners immediately.

Starfleet regulations require that prisoners be treated well, and that all of their life-support needs be met. In the case of non-Federation citizens, the crew should make every effort to contact the proper authorities of the prisoner's home world, although prisoners accused of crimes against Federation personnel or property should be held over while Federation authorities discuss matters of extradition with the prisoner's home civilization.

For escaping from a Starfleet (or similar) brig, see the rules in this chapter and information in Chapter Six.


One of the prime security measures is the use of sensors, devices able to pick up and monitor certain types of information, sending out an alarm or activating other security measures when they detect intruders.

Sensor technology in the 24th century is capable of picking up nearly every type of energy in the electromagnetic spectrum (and some exotic energies outside of it), along with biological matter, and even specific DNA sequences. Most sensor packages consist of multiple types of sensors, each detecting something different. For example, a sensor suite might scan for electromagnetic disturbances, ionization traces (indicative of a transporter beam), infrared signatures for body heat and working machinery, and so forth.

Visual Sensors

Visual sensors transmit a visual image of the area they are set to scan, similar to old-fashioned security cameras. They can be crudely overcome by blacking them out with some opaque material (paint, for example). A more sophisticated option is to install a device that feeds the sensor's data back into it, creating a "loop" and effectively blinding the sensor.

Motion Sensors

Motion sensors detect molecular displacement traces created by moving objects. The sensors generally have a "threshold" of movement they are designed to detect. If the threshold is set too low, the random movement of air molecules can be enough to set the sensors off. Low-grade motion sensors can be evaded by moving very slowly (a Challenging Stealth (Stealthy Movement) Skill Test). Otherwise, it easiest to defeat motion sensors by overcoming the computer that controls them (see Computer Systems).

Infrared Sensors

Infrared (or IR) sensors pick up infrared radiation or heat sources, including the body heat of warm-blooded lifeforms. Characters can overcome them by wearing special anti-IR clothing to masks their heat signature, or by programming a device like a tricorder to emit an IR scattering field (a Challenging Personal Equipment (Tricorder) Skill Test).

Electromagnetic Sensors

These sensors detect electromagnetic disturbances of various kinds, including the operation of certain devices, the use of energy weapons like phasers, and so forth. They can be avoided by not using any high-energy devices, although this can make overcoming other sensors more difficult. Characters can also use technology to shield electromagnetic impulses, preventing them from being picked up by the sensors.

Subspace Sensors

These sensors are fairly rare, they detect disturbances in the subspace field, such as those caused by warp nacelles or a transporter beam. They can detect anyone beaming in or out of an area, and provide information to help track the transporter beam's source. Subspace sensors are difficult to overcome, but a Difficult Shipboard Systems (Transporter) Skill Test can slip a transporter beam in "between" sensor cycles.

Starship Sensors

Starships rely heavily on the data provided by their various sensors for tactical and navigational decisions. Without its sensors, a ship is effectively blind and deaf, unable to detect anything except by having someone go to a window and look out. Therefore, many tactics in starship combat are based on fooling or shutting down an opponent's sensor systems.

Sensor Interference

There are a number of ways of evading sensor scans. The most basic is using some form of matter or energy as "cover" to interfere with the sensors' operation. Normally, the tactical officer makes a Moderate (7) Shipboard Systems (Sensors) Skill Test to obtain a sensor lock on an opposing ship. Interference increases the Difficulty of this Test, making it harder to lock on to the opposing ship.

Examples of interference include things like the following:

  • Asteroids or other space debris laden with heavy metals that confuse sensors. This also includes intentionally manufactured "chaff" released into space to confuse a ship's sensors.
  • Nebular clouds containing sensor-screening elements and electromagnetic interactions that block sensors. Ships operating in such a cloud are virtually blind.
  • Powerful electromagnetic and subspace energy fields, such as the radiation of an unstable or flare star, or even the magnetic field of a planet's poles. These energies make it difficult for the sensors to detect anything.

The Narrator should decide how much any given type of interference increase the Difficulty of Shipboard Systems (Sensor) Tests, at least by one level of Difficulty, sometimes more. In effect, the interference serves as a kind of natural "cloaking device" for the ship, with a rating determined by the Narrator.

The main drawback of most methods for interfering with an opponent's sensors is they interfere with the sensors of both ships, leaving them both stumbling around, effectively blinded. Fighting in a nebula is like two combatants fighting in a darkened room. In some cases, character with more experience dealing with sensor interference may still find it to their advantage, and it's preferable to being destroyed by a superior vessel.

Fooling Sensors

In some cases it is possible to not only block an opponent's sensors but to fool them entirely, feeding them false or misleading information. Usually, this involves gaining access to the opposing ship's computer system (see Computer Systems, above) and sending false input codes to the sensors. This allows the character to make the sensors "believe" just about anything; enemy ships where there are none, system failures or problems that don't really exist, and so forth. Characters on the opposing ship realize the image is false when it doesn't live up to their expectations (the enemy ships don't open fire, the failed system continues to function, and so forth). A crewmember can also realize the computer's error with a Moderate (7) Shipboard Systems (Sensors) Test.

There are also other, somewhat cruder, means of sending false signals to an enemy ship's sensors. One is to modify the signals sent out by your own ship, giving the enemy false impressions about it. This is usually accomplished by modulating the shields, altering transponder frequencies and signals, and modifying warp field signature. A Moderate (7) Test using the appropriate Engineering skill can modify one of the ship's systems to send a simple false signal, like making the warp signature of a Federation ship appear Klingon, for example. A Challenging (10) Test can significantly alter the ship's signals, making a Federation starship appear as a Cardassian cargo-hauler to all but visual sensors. A Difficult (13) Test even provides some screening against visual sensors, but cannot fool them entirely. Still, combined with some Fast Talk and a communications filter (see Communications), this can go a long way.


One of the most difficult security and surveillance measures to avoid is the use of psionic abilities, particularly telepathic skills, in detecting criminal or subversive thoughts. Telepathy is not commonly used in espionage or security work. Federation law forbids telepathic scans of unwilling subjects, although Federation telepaths have sometimes detected criminal plots purely by chance, picking up on the surface thoughts of the criminals before they carried out their scheme. Ambassador Lwaxana Troi of Betazed once foiled a plan by the Antedeans to bomb the Pacifica diplomatic conference in this way.

Since there is no known technological means of blocking telepathy there are only two methods of evading telepathic security. The first is training in the Mind Shield skill (ST:TNG, p. 99), increasing resistance to telepathic scans and allowing the user to keep his surface thoughts well hidden. Since telepathic scans are used only rarely in security work, this usually suffices to protect the character from casual detection.

The second option is to control the amount of information known to the people involved in a criminal plot. If an underling doesn't know something, he can't reveal it, even under a deep telepathic scan like a mind meld. Espionage organizations like the Tal Shiar and the Obsidian Order have also been known to give their agents suicide devices, allowing them to kill themselves before they can be interrogated.

Finally, some species, like the Ferengi and the Breen, are naturally immune to telepathic detection. Species like the Betazoids that rely on telepathy in their dealings with other races are often uncomfortable around such lifeforms.