I was doing the warp convergence exploration thing. I warped to a safe space and I activated the filament and was in the “space”. After I was done, I exited the space and was immediately ganked by two awaiting ships in K space.
How did they find me? or rather how did they find the filament trace if I was at a space spot?
If I recall correctly you need combat scan probes (so not the regular core probes that you use to scan down cosmic signatures) to scan down filament traces.
There are several tactics regarding traces. When you come out you have a moment of invincibility. You can actually activate a new filament if you time it right and get away by going into another one. Of course you’ll come out again eventually. They can prevent you from doing so by anchoring a mobile depot as you’ll be too close to it.
In high sec there are some systems where you can’t anchor a mobile depot but you still can use the filament. Also if you have an alt the alt could shoot the ganker to preemptively call Concord. You can also warp in a bowhead or other ship that has a hangar and quickly store your ship before they can gank you. Then they likely aren’t prepared for the much higher tank on the storage ship. Etc.
If not in high sec then doing the filament at a deep safe (further than max dscan range from all celestials) in an empty system can help. You can see a trace on d scan. However if someone enters system, sees no one in local, and no trace on d scan, likely they won’t waste their time combat probing for the off chance a trace they can’t dscan might be there.