Security technology

== Communications ==
One thing that can be difficult to secure is communications. A transmission can be overheard by anyone with a reciever tuned to the proper band, making communications vulnerable. A number of technological solutions have been developed to keep communications and prevent eavesdropping, but for every technique of covert communications, there is a way around it.
=== Encryption ===
Encryption is a complex mathematical algorithm that scrambles the information content of a transmission. The reciever 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. 
=== Piggybacking ===
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.
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.
== Computer systems ==
The center of nearly every security system in the 25th century is a computer. 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.
=== Transponder signals and prefix codes ===
See: Transponder and prefix codes
=== Starfleet security codes and data access ===
See: Starfleet security codes and data access
=== Locks ===
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.
=== Sensors ===
One the primary 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 25th 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. Otherwise, its easiest to defeat motion sensors by overcoming the computer that controls them.
=== 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.
=== 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.
=== 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.