It appears that spammers have found a way of automatically creating
Hotmail and Yahoo email accounts, having already created more than
15,000 bogus Hotmail accounts, according to security company BitDefender.

Both Microsoft and Yahoo use “captcha” systems to stop email
accounts from being automatically generated; accounts aren’t created
until a new user correctly identifies letters depicted in an image.
Captcha systems are designed to ensure that the letters are not easily
recognized by machines.

BitDefender says that a new threat, dubbed
Trojan.Spammer.HotLan.A, is using automatically generated Yahoo and
Hotmail accounts to send out spam email, which suggests that spammers
have found a way to overcome Microsoft’s and Yahoo’s CAPTCHA systems.

Story continues at tech.blorge.com