SETI has been looking for radio signals from ETI for over 50 years with no results yet.
Many have argued the SETI search paradigm is wrong for various reasons and that they should broaden their operations somewhat. Looking for interstellar optical beacons is one of them.
Below is a photo of a possible beacon in the open cluster NGC7789, taken 18 months apart. Well, you decide:
The photo below (click link) is an animation of two images of open cluster NGC7789 (in the constellation Cassiopeia), taken around 18 months apart, from the New Forest Observatory, Hampshire, U.K. The star sitting just below the open cluster has changed in magnitude during this period from about magnitude 7 (brightest) to approximately magnitude 14 (dimmest). This impressive variable star (WY Cas) sure appears like it’s trying to get our attention. According to Roger Pickard of the British Astronomical Society, W Y Cass does indeed vary by something like 7 magnitudes over a period of about 18 months! So, no aliens this time, but instead rather an incredibly interesting object all the same.
(You have to click on the site link below and click on the photo there to activate the beacon.)