The Luminoth security sensor probe is a Luminoth device used to gather data. During their war with the Ing, it appears that devices such as these were hijacked by the enemy for their own use, likely during the time when the machines joined them.
One of these is located in the Central Area Transport East within the Sanctuary Fortress. It is possible that the Ing and the rogue machines used this to gain information on Samus as she traversed the region, as well to gain more info on the Space Pirates that assaulted the fortress before her.
"Object analysis complete. This is a Luminoth security sensor probe. The probe is active. Its transmissions are being monitored by numerous sources. Enemy forces may be using the probe to collect intelligence data."