A class-5 intelligence drone was a type of Federation sensor drone used for intelligence-gathering purposes.

In 2373, two such drones were stationed in the vicinity of Portas V. During his hunt for the Maquis defector, Michael Eddington, Captain Benjamin Sisko ordered that their sensor logs be retrieved in order to find out who had recently visited the planet. (DS9: "For the Uniform")

Star Trek: The Next Generation Technical Manual (p. 117) suggests that the class-5 intelligence drones are modified class-5 probes. On page 117, class-5 probes are said to be fully autonomous in executing their missions and can be modified for tactical application with the addition of a customized sensor countermeasure package.
Star Trek Encyclopedia (4th ed., vol. 1, p. 145) depicted the class 5 intelligence drone as looking like the interface probe.
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