A Chameleon field was a highly advanced piece of technology that was employed by the Chodak race.
These were a complex masking technology that sent false readings to external devices allowing the object emitting the field to camoflage itself as another object. As such, a device containing such a field was capable of disguising itself as an asteroid or part of station. However, a noted problem with the chameleon field was the fact that it took a second to match external sensors.
One method of combating this technology was through the use of randomly shifting sensor frequencies which served as a way of combating the field's effects.
In 2370, the Chodak dispatched one of their sophisticated probes to the Mertens Orbital Research Station where it embedded itself deep within the outpost and disguised itself as part of its surroundings. After the attack, the USS Enterprise-D was dispatched by the Federation to discover the source of the attack in the Cymkoe IV system. An away team discovered the probe attached in the engineering section which disguised itself as part of the conduits. After its discovery, the probe departed the station and adjusted its chameleon field to appear as an asteroid to the Enterprise. (TNG video game: A Final Unity)