The origin of the malware attacks was reported by Bloomberg News, which cited as sources two people familiar with the invasions. Investigators tracked at least one server being used by the hacker ring to a hosting company in the Ukraine, Bloomberg said.
The high-tech companies say they did not lose any data in the breaches and they are working closely with law enforcement. Those efforts include investigations by the FBI and the Secret Service, Bloomberg reported.
"There is no evidence that any data left Apple. We are working closely with law enforcement to find the source of the malware," a statement released by Apple said.
Facebook acknowledged that it was attacked last week. It said no user data had been compromised, but that many other companies had been targeted in the same attack. Reuters said the hackers were traced to China.
The attack on Twitter resulted in the breach of as many as 250,000 users' data.