Emails, supposedly from the Internal Revenue Service, have been used to glean sensitive data from U.S. taxpayers.[64] While the first such examples were sent indiscriminately in the expectation that some would be received by customers of a given bank or service, recent research has shown that phishers may in principle be able to determine which banks potential victims use, and target bogus emails accordingly.[65] Social networking sites are a prime target of phishing, since the personal details in such sites can be used in identity theft;[66] in late 2006 a computer worm took over pages on MySpace and altered links to direct surfers to websites designed to steal login details.[67] Experiments show a success rate of over 70% for phishing attacks on social networks.[68] 2007 3.6 million adults lost US$3.2 billion in the 12 months ending in August 2007.[69] Microsoft claims these estimates are grossly exaggerated and puts the annual phishing loss in the US at US$60 million.[70] Attackers who broke into TD Ameritrade's database and took 6.3 million email addresses (though they were not able to obtain social security numbers, account numbers, names, addresses, dates of birth, phone numbers and trading activity) also wanted the account usernames and passwords, so they launched a follow-up spear phishing attack.[71] 2008 The RapidShare file sharing site has been targeted by phishing to obtain a premium account, which removes speed caps on downloads, auto-removal of uploads, waits on downloads, and cool down times between uploads.[72] Cryptocurrencies such as Bitcoin, introduced in late 2008, facilitate the sale of malicious software, making transactions secure and anonymous.