Microsoft's anti spyware software has become the target of phishers after people's bank account details.

The BankAsh-A Trojan horse is designed to steal online banking passwords from UK online banks such as Barclays, Cahoot, Halifax, HSBC, Lloyds TSB, Nationwide, NatWest, and Smile.

At the same time, it also disables Microsoft AntiSpyware, currently available only as a beta download.

Security experts at Sophos said the Trojan tries to suppress warning messages that Microsoft AntiSpyware may display, and deletes all files within the program's folder.

"This appears to be the first attempt yet by any piece of malware to disable Microsoft AntiSpyware, but it may be the first of many such future attacks," said Graham Cluley, senior technology consultant for Sophos.

"As Microsoft's product creeps out of beta, and is properly released and increasingly adopted by the home user market, we can expect to see more and more attempts by Trojan horses, viruses and worms to try and undermine its effectiveness."