Anti-virus company Sophos has discovered the first piece of malware targeting Microsoft's new anti-spyware product, which is still in beta.
Sophos said the BankAsh-A Trojan horse is designed to steal online banking passwords from unsuspecting Windows users. The Trojan horse also disables Microsoft AntiSpyware, currently available only as a beta download from Microsoft's website.
The Trojan also attempts to suppress warning messages that Microsoft AntiSpyware may display, and is designed to delete all files within the program's folder.
"This appears to be the first attempt yet by any piece of malware to disable Microsoft’s 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 users, we can expect to see more and more attempts by Trojan horses, viruses and worms to try and undermine its effectiveness."
The BankAsh-A Trojan also targets users of UK online banks such as Barclays, Cahoot, Halifax, HSBC, Lloyds TSB, Nationwide, NatWest and Smile, said Sophos.
The British banking industry has published information about how online bank users can help stay safe online at www.banksafeonline.org.uk