Although some characterize it as a curse, in reality “pulsa de nura” (Aramaic for “bolt of light”) is a prayer: it is a prayer beseeching God to deliver judgment on someone if that someone has sinned greviously against God. This is not taken lightly at all, and evidently even secular / atheist / agnostic / inactive / non-religious Jews dread it.
Many rabbis deny it exists. One Chicago rabbi published the text (as a PDF file) on his website, in order to dispell rumors about it.
The prayer is tied to Kabbalah (the real kind; in other words: Jewish mysticism or esotericism; to be more accurate, popular practical Kabbalah, which tends a bit to the superstitious side), and as such probably involves pronouncing or spelling names of God, petitioning angels, and so on. (I downloaded the PDF but have not read it; in any case, it would probably be in Aramaic, which I know very little of. Were it in Hebrew, I would have be able to make out what it meant.)
Evidently, the text for it is not easily found (probably because people fear misusing it: if misused, the person performing the prayer could be severely punished) or is not very common, but is used commonly in ultra-Orthodox circles against politicians they oppose. (As such, it would be found mainly in books circulating in ultra-Orthodox esoteric circles.)
But here is the puzzling part about it: there have been two well-known instances recently when pulsa de nura was used. The first time was against Yitzchak Rabin; he was assassinated within a month’s time. (I remember reading reports about the prayer, and then soon thereafter of the assassination.) The second time was against Ariel Sharon; he was felled by two major strokes within six months. (I remember reading about the prayer and expecting something very bad to happen to Sharon, all appearances to the contrary at that time. Then,…)
Although people dismiss these as simple coincidences, I don’t know if I am so sure about that. Even Sharon’s health was extraordinarily robust before he was mysteriously struck.
(I should do a post on Jewish esotericism: explain what it’s really about. None of this Kabbalah Centre nonsense.)