A signal detected by China's FAST radio telescope has raised questions about its origin. The signal, named NBS 260108, was identified at a frequency of 1148.4167 MHz and points toward K2-155, a red dwarf star located 238 light-years away. The signal was discovered during a re-examination of observations from the FAST telescope, which had previously studied 33 exoplanetary systems. Out of 139,127 raw detections, this was the only new candidate that passed all filters. The data had been stored on hard drives for five years before being reviewed again. In 2021, the FAST telescope listened to 33 stars known to host planets. A first analysis, published in 2022, had already detected something in the direction of the star Kepler-438, but it was later determined to be interference from Earth. A team led by Zi-Qi Li from Beijing Normal University and Zhengzhou University re-examined these recordings using artificial intelligence trained to detect technosignatures—potential signs of technology from alien civilizations. The machine initially raised 139,127 alerts. After applying several filters, only two remained. The first was the previously identified false lead from Kepler-438. The second was entirely new, with a frequency so clear that it seems manufactured. The signal named NBS 260108 is on an extremely fine frequency, 1148.4167 MHz. Another detail is that this frequency shifts very slightly during the observation, which is exactly what one would expect from an emitter located on a planet. The FAST antenna listens to the sky using 19 sensors, or beams. The central beam targets the studied star, while the other 18 monitor the surroundings. If the signal were from Earth, it would appear in all beams. However, NBS 260108 appears only in the central beam, suggesting it may not be terrestrial interference. K2-155 is a red dwarf, a star smaller and cooler than the Sun, located 238 light-years away. It has three super-Earths—planets slightly larger than Earth—discovered in 2018 by the Kepler space telescope. The farthest one, K2-155d, is 1.6 times the size of Earth and completes its orbit in 40.7 days, at the edge of the zone where liquid water could exist on the surface. The same signal pattern reappears around three other stars: Ross 128, K2-18, and GJ 9066. However, a real source installed around K2-155 cannot manifest itself in three different directions at the same time. The authors estimate that human interference or a malfunction of the equipment remains the most likely explanation, even though they have not been able to identify its exact source. NBS 260108 remains officially unclassified. The main achievement of this work is the filtering method used, which can scrutinize hundreds of thousands of alerts and is reusable on other radio telescopes.