The damage done by the attack on Sony’s PlayStation Network last month—an event that exposed personal information on 100 million accounts—is still being calculated, but was magnified when Sony offered only delayed and incomplete information to users, some experts say.

Sony faces numerous Congressional requests, including this one made last week—as well as subpoenas from New York’s attorney general—seeking more information about what information was stolen, and the nature of its security defenses.

Howard Stringer, chief executive of Sony, has said the breach is the largest of its kind ever experienced by a company. But the details of the attack are still largely murky. “We have this problem with all such attacks. We never know what happened, how bad it is, what they did, or how they did it. Nothing,” says Bruce Schneier, a renowned security expert. “There is no visibility at all, and Sony is particularly ham-fisted about saying stuff and then retracting it.”

In a response to an earlier letter from Congress, Sony said it faced an “extraordinary” situation in which information about the intrusion “was neither immediately nor easily obtainable,” and it acted prudently in shutting the network down quickly while investigating what had happened.

Sony shut down the PlayStation Network from April 20 until May 15, when the company started getting its networks back online. Sony estimates that the incident cost $171 million.

Although the attack started sometime between April 17 and April 19, it wasn’t until April 26 that Sony announced that massive amounts of personal information had been exposed. For seven days, Sony made only cryptic statements to explain network outages. On April 20, the company published a one-line blog post saying: “We’re aware certain functions of PlayStation Network are down. We will report back here as soon as we can with more information.”

On April 21, Sony said it was still investigating. On April 22, it said there had been an “external intrusion on our system.” On April 23, it said it was “rebuilding our system to further strengthen our network infrastructure” in part to “provide the system with additional security.”

Three days later, Sony finally issued a more detailed statement on the hack, confirming that names, addresses, birthdates, e-mail addresses, and other information for registered users of its PlayStation Network and Qriocity—which provides streaming media—had been stolen. It gave customers advice on how to protect themselves in case of identity theft.

Later that day, an angry user named “jonabbey” commented on Sony’s PlayStation blog: “It’s rather incredible that this is the first meaningful communication you have given us. Many of us who are savvy enough to be reading your blog are technical enough to be running our own Internet services, and you really can’t go wrong by over-communicating, here.”

Schneier agrees. “You need enough information so researchers—and also customers—can make intelligent decisions,” he says. “But the companies don’t want the customer to have visibility. They are perfectly happy not talking about the details, because the details are embarrassing.” 

Schneier added: “Right now, you as a customer have no choice but to trust Sony— or Citibank, or your phone company, or Facebook, or Amazon, with your information—and you have no visibility and no control over how they secure it.”

Last week, the White House announced a legislative proposal that would increase penalties for those who hack into computer systems—but only if the target involves critical infrastructure, which is yet to be defined.  Under the current Computer Fraud and Abuse Act, penalties only apply to attacks on  financial or government networks. Melissa Hathaway, a consultant who served as President Obama’s cyber policy advisor in early 2009, says the proposal should extend to incidents such as the Sony breach. 

“This is an opportunity to actually create more of a domestic deterrence policy statement that any computer that is penetrated for whatever reason should fall within this law,” Hathaway says. “The laws should determine that the hacking is illegal, and that the effects of the hacking should determine the penalties. It’s time that the government declares that the computer systems of all entities—government, commercial, education—are interconnected.”

The White House proposal would also create a federal law requiring companies to notify users of breaches that expose their personal information in the United States. Currently, a patchwork of 47 state laws govern such notification.