Holographic masking system

The Holographic masking system is a type of stealth technology used to create a false image of a starship for purposes of stealth and deception.

Conceptually the process is quite simply, the vessel selects a preferred identity and then uses its array of holographic emitters to create the image of that ship around its self, presumably the technology is somewhat more sophisticated so that the user might take on the appropriate warp field frequency and other markers that would give away its true origins.

History
Holographic technology has been utilised throughout history as a means of disguise and deception but it was not until the 22nd century that anyone conceived of using it to falsify the existence of a starship.

Romulan Drones
The Romulans were the first to use the idea, deploying a number of remote drones to carry out attacks on other vessels. They utilised the system to take on the identity of other species vessels in the hopes creating tensions between usually amicable races. The earliest deployments of these vessels were thwarted by the Starship Enterprise NX-01, and in fact resulted in a greater feeling of unity between the species the Romulans were hoping to propel into war. Whether or not the Romulans continued to use the vessels or the holographic systems for similar or alternative purposes is unknown. (Enterprise episodes: Babel One, United and The Aenar)

USS Incursion
In the 24th century the Federation developed there own version of the system (whether or not they took inspiration from the earlier Romulan usage is unknown) which was deployed on the USS Incursion, a Starfleet Intelligence vessel which used the system to go undercover into enemy territory. The ability to hide amongst there enemies was a crucial factor in the Incursion’s successful defeat of the Wardens in 2377 (Game: Away Team) and later they were a crucial cog in the war with Species 8472, taking on the identity of 8472 vessels to infiltrate their space and locate installations (Game: Armada II).