Investigators began looking at the attacks several months ago, and when the Department of Homeland Security issued a vaguely worded warning this month, a government official told The New York Times that “most everything we have seen is coming from the Middle East.” They said the evidence was not specific enough to conclude with confidence that the attacks were state-sponsored, but control over the Internet is so centralized in Iran that they said it was hard to imagine the attacks being done without government knowledge. While the attackers have been unsuccessful to date, they have made enough progress to prompt the Homeland Security warning, which compared the latest threat to the computer virus that hit Saudi Aramco, the world’s largest oil producer, last year.