This is a timeline of major events associated with the attack on Sony's PlayStation Network and Qriocity online services.
Dates are given relative to announcements from Sony Computer Entertainment's headquarters in Tokyo. Dates corresponding to announcements from Sony's U.S. unit are provided in parenthesis.
Wednesday, April 20 (Tuesday, April 19, U.S.)
Sony learned its PlayStation Network and Qriocity networks had been compromised. At the time, the company did not announce this. It was subsequently disclosed in a statement issued from the company's U.S. subsidiary on April 26.
Thursday, April 21 (Wednesday, April 20, U.S.)
Sony took its first public step by closing down the two networks, but it didn't disclose what it already knew: the networks had been hacked. It issued a statement that said, "We're aware certain functions of PlayStation Network are down. We will report back here as soon as we can with more information."
Friday, April 22 (Thursday, April 21, U.S.)
The company said it was still investigating the cause of the outage and that it would be "a full day or two" before everything is back to normal.
A posting on Sony Europe's PlayStation blog suggested the networks had been attacked. The posting was later removed, but numerous gaming news outlets reported it as saying, "Our support teams are investigating the cause of the problem, including the possibility of targeted behavior by an outside party."
Saturday, April 23 (Friday, April 22, U.S.)
Sony revealed for the first time the cause of the problems. "An external intrusion on our system has affected our PlayStation Network and Qriocity services. In order to conduct a thorough investigation and to verify the smooth and secure operation of our network services going forward, we turned off PlayStation Network & Qriocity services," it said in a statement. It offered no details on when services might return to normal.
Hacking group "Anonymous" said in a statement that its core had nothing to do with the attack, but the message left open the possibility that individuals from the group might be responsible. "While it could be the case that other Anons have acted by themselves AnonOps was not related to this incident and takes no responsibility for it," the statement said. It accused Sony of taking advantage of previous attacks on its network to explain an internal problem with company servers.
(Read more: PlayStation Network Enters Third Day of Outage)
Sunday, April 24 (Saturday, April 23, U.S.)
Sony said it was having to rebuild its network as a result of the attack. "Our efforts to resolve this matter involve rebuilding our system to further strengthen our network infrastructure," the company said in a statement. "Though this task is time-consuming, we decided it was worth the time necessary to provide the system with additional security."
The company said it was "working around the clock to bring them both back online," but didn't say when they might return. "We thank you for your patience to date and ask for a little more while we move towards completion of this project," the statement said.
(Read more: Sony "Rebuilding" PlayStation Network After Attack)
Monday April 25 (Sunday, April 24, U.S.)
For the first time since the problems began, Sony's headquarters went a day without releasing an update.
A spokesman for Sony in Tokyo told IDG News Service a "thorough investigation" was under way. He said the company had not yet determined whether the personal information or credit card numbers of users have been compromised, but that Sony would promptly inform users if it found that was the case.
Tuesday, April 26 (Monday, April 25, U.S.)
Computer security experts called in by Sony concluded a breach of consumer data had occurred when the PlayStation Network was hacked. At the time, the company held off on making the announcement until the next day.
Kaz Hirai, head of Sony's gaming division, appeared at a Tokyo news conference held to unveil the company's tablet PCs. Hirai expressed condolences and support for victims of the March earthquake and tsunami, talked about the new tablets and how they could download content from the Qriocity online service, but failed to mention the problems with Qriocity and the PlayStation Network. He left the stage without taking questions, as originally scheduled.
Separately at the same event in Tokyo, Sony representatives said there was no new update on the situation and no estimate for a return of the service.
Wednesday, April 27 (Tuesday, April 26, U.S.)
Sony released its most detailed statement to date on the hack and confirmed that personal information was stolen. The information included names and addresses for registered PlayStation Network and Qriocity users, along with their birth dates, e-mail addresses and other personal information.
"While there is no evidence at this time that credit card data was taken, we cannot rule out the possibility," Sony said. It advises customers to create credit card fraud alerts and keep a close eye on charges made to linked credit cards.
It also said the PlayStation Network and Qriocity would be back online "within a week."
Sony shares fell 2 percent on news of the potentially huge data leak, ending Wednesday trading in Tokyo at 2,366 yen, down 49 yen.
(Read more: Sony: PlayStation Network Personal User Data Stolen)