(Reuters) - Technology news website TechCrunch published on Wednesday sensitive internal documents belonging to Twitter, including financial projections, offering a rare glimpse into the wildly popular microblogging site.

Twitter has a targeted revenue run rate of $140 million by the end of 2010, with the expectation it would record its first revenue -- a modest $400,000 -- in the third quarter of this year, according to a document Techcrunch published that it said was sent by a hacker.

Dated February, the document was labeled a Financial Forecast and outlined how Twitter expected to take in $4 million in revenue by the fourth quarter and maintain $45 million of cash in the bank.

By the end of 2013, Twitter hoped to sign up 1 billion users, post $1.54 billion in revenue, employ 5,200 people and make $111 million in net earnings, according to TechCrunch.

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Techcrunch, which said it negotiated the publication with Twitter itself, added in the report that the document was unofficial and "certainly no longer accurate."

Twitter was not immediately available to comment on the projections. The document published by TechCrunch did not provide details about how Twitter planned to get the revenue.

"We are in touch with our legal counsel about what this theft means for Twitter, the hacker, and anyone who accepts and subsequently shares or publishes these stolen documents," Twitter said in an official blog post.

TechCrunch said earlier on Wednesday that an anonymous hacker had gained "easy access" to hundreds of pieces of internal Twitter information -- from pass codes to meeting minutes -- and then forwarded the data to the news website.

TechCrunch initially posted a single document, a discussion about a proposed reality television show. Within hours of its posting, hundreds of readers condemned the site for the move.

Michael Arrington, founder and co-editor of TechCrunch, defended its right to make the material public, saying it would exercise restraint on material such as personnel records.

"We've spent most of the evening reading these documents. The vast majority of them are somewhat embarrassing to various individuals, but not otherwise interesting," Arrington wrote.

"But a few of the documents have so much news value that we think it's appropriate to publish them."

Twitter, which permits users to post "Tweets" of up to 140 characters, has won a loyal fan following of millions and catapulted to prominence after it was used by protesters in Iran following a disputed election there.

The company is trying to parlay the popularity of its free service, into a money-making business. Twitter co-founder Biz Stone told Reuters earlier this year the company had decided to generate revenue in 2009, a year earlier than planned.

Stone also said Twitter was more interested in generating revenue from premium add-on features, such as analytic tools, than from traditional online advertising.

Twitter's surge in popularity, and its real-time search feature, have captured the attention of Web giants such as Google Inc, which has had unspecified discussions with the company, according to Google CEO Eric Schmidt.

"Obviously Twitter is a very attractive target for hackers or attackers, because of its high profile as a very popular media website," said Joris Evers, a spokesman and security expert at McAfee, which protects against Internet threats.

(Additional reporting by Alexei Oreskovic; editing by Richard Chang and Andre Grenon)