Due to the location of the "graffiti" - the Hagia Sophia, if I'm not mistaken - I would say that it was most probably made by Scandinavian mercenaries, known as Varangian, rather than by raiders. Some of them were adopted as elite soldiers in the Byzantine army in the early 10th century, forming the Varangian Guard.

The distance isn't that large if you take in consideration that they navigated the eastern European rivers (map). Some of those traders and raiders eventually settled along the rivers and intermingled with the local Slavic populations. Rurik was one of the chieftains that settled and founded the city of Novgorod and the Rurikid dynasty.

Anyway, this is only a bit of information I think that may help you understand some basic points. I can't cite any concrete sources on this, as I'm speaking from memory. You should wait for one of the flaired users for more detailed information.

Edit: typo

Source of the picture? I don't see it anywhere.

They really did raid Byzantine sites, and to some extent even tried to raid Byzantium itself. But the vikings also simply traded and otherwise dealt peacefully with the Byzantine empire, which was their southern neighbour in the east after all.

This seems very strange now, but the point is that during this time Russia as a state did not exist, and one of the vikings' most succesful projects was the colonization of western Russia, in what they indeed called the kingdom of Rus.