I'm a bit worried about this, as I did not noticed this situation until not too long ago.

I'm using a Canon 600D (EOS Kiss X5 in Japan, EOS Rebel T3i in the US), and I've noticed (And tested) that, when taking a long exposure shot on a night environment (Edit: and on a not dark environment, its just harder to spot), a fixed pattern of bright pixels appears on the shot. These points can be seen on the in-camera preview, so I don't think is a problem from the software I'm using for post processing.

It does not matter the ISO value (Although I think with lower ISO values there's less points), the pattern appears when the shutter speed is slower than 10", and it does not matter if the lens cap is put on the lens.

I bought the camera on 2014 and I've been shooting on and off since. The latest long exposure shots I recall are from last year and did not featured these points. I've done a bit of concert photography (maybe bright lights going striaght to the sensor), but nothing more "dangerous" in any way I can think of.

Any suggestions on what to do, if there's something that can be done to fix this? Thanks!