Informer

Informers are Grineer spy drones introduced in the Spy Drone Event starting on July 5th, 2013. They appear as miniature weather balloons that float in place on random points of the map. Informers cannot attack, or even move aside from hovering slightly in the same space. Informers are equipped with Orokin cloaking tech, which they will activate upon being damaged and escape, meaning they must be killed with the first shot.

Informers have the special ability of disrupting the player's minimap when in its proximity, which is also an effective way of knowing when one is nearby. They can also negate Enemy Radar at a radius slightly larger than its minimap disruption radius.

During the duration of the event, Informers will be found on any Grineer missions that are level 15 or above. Killing 20 will qualify the player for receiving the Snipetron Vandal as a reward after the event ends. They can be often found on Grineer systems above level 15 (Earth, Sedna, Ceres) in Grineer missions, Especially on Cambria (Earth).

Trivia

 * Informers will disappear upon receiving damage from Grineer units as well.
 * Informers will respond to your movements and can "see" you, turning towards your direction while staying in the same postition.
 * Given a long enough radar range, it is possible to detect an Informer with Enemy Radar by staying out of its range with altitude.
 * Informers spawn on ground level, before floating up to its proper height.
 * Banshee's Sonar can spot them even when your map is almost completely disrupted by them.