REDMOND, Wash. -- Microsoft ( MSFT) has joined the list of prominent technology companies confirming they have been hit by a recent computer hacking attack.In a blog posting Friday, Microsoft said it had found no evidence that any customer data had been heisted. Microsoft Corp. gave few other details about the break-in, except to say that was it similar to a hacking attack that online social networking leader Facebook Inc. ( FB) disclosed last week. Facebook had said its investigation had discovered other companies had been hacked, but didn't identify the other victims. Like Facebook, Microsoft says it is still investigating how malicious software was planted on what it said were a small number of its computers. Online messaging service Twitter also recently disclosed that hackers may have stolen information about 250,000 of its users.