Symantec has warned of a Trojan aimed at users of Windows 95, 98, 2000, NT and Server 2003 posing as an activation program and designed to steal credit card information.

Symantec's Takashi Katsuki says Trojan.Kardphisher is not very technical, but that the author has gone to great lengths to make it appear legitimate.
When your restart your PC after the Trojan is installed, Katsuki says, an official-looking screen appears stating the user's copy of Windows was activated by someone else. "To help reduce software piracy, please reactivate your copy of Windows now," reads the screen. "We will ask you for your billing details, but your credit card will NOT be charged."
Katsuki explains: "You can only choose Yes or No. You can't run Task Manager or any other applications. If you choose No your PC will be shut down immediately."
If you choose Yes, though, a second screen then asks the user to enter his name and credit card details which are then forwarded to the hacker's server.
"Now you may think: 'It can't be true. I have activated my legitimate copy of Windows. Microsoft can't do such a thing!'," says Katsuki. "Surely almost everyone will notice that something strange is going on, and hopefully very few people will actually become victims by inputting their credit card details. But, unfortunately, even the people who are not tempted to give up their information this time might well become victims the next time. After all, failure to follow the on-screen instructions results in your PC shutting down immediately.
"This Trojan teaches us all a good lesson – trust no-one," adds Katsuki. "This is the slogan from the TV show The X-Files, and very much applies when it comes to protecting your personal information. Sometimes the creators of Trojans attempt to impersonate Microsoft, a bank, or even a government organisation. Whatever the warning or message says, we must make very sure it is genuine before giving up any personal details, financial or otherwise.
"It's far better to doubt a genuine request until proper verification is provided, than it is to blindly place your trust in a communique simply because it appears to have come from a trusted source.
"Sad though it may be, the days of leaving your front door unlocked are over," he says. "In these times we not only need a lock on the door, we need a security guard watching the front door, the back door, and everywhere in between."