Someone wrote to me asking who the masked ninja in episode 68 is.

Unfortunately, I don't have an answer. The scene does not appear in the manga, thus the character is not listed in the data books. No name, age or rank, nothing is known about this character.
The end credits of the episode list three names as "Konoha nin": Watanabe Hideo (n pY), Harada Masao (c v) and Misono Yukihiro (䉀 sm). All three have had more than the one minor part, adding further proof of the insignificance of our masked hero.
He appears for a few seconds near the end of the first half of the episode, throws some kunai with explosive tags at a giant snake, then there's some blood and a scream and we don't really get to see what happens.

Lastly, in the funeral in episode 80, there are six portraits beside Sandaime's; one of them is of a masked ninja. (In the manga, there aren't any other portraits than Sandaime's.)

On the other hand, I'm pretty sure Konoha lost more than six ninja in the attack. Those six must've been pretty special to be honored alongside the Hokage.