It can brighten even the drabbest Monday; everyone, it seems, likes getting an E-Card greeting in their inbox. However, a fake E-Card that's currently being spammed worldwide can unleash a nasty computer virus.

The greeting looks real enough. It is an exact replica of a Hallmark E-Card, or one from or a number of other sites that provide animated email greetings.

The recipient is instructed to click on a link to view the greeting card. There may also be instructions for downloading and saving it. But doing so could lead to big trouble.

The link goes to a hackers Web site and tries to open a file called postcard.exe. Security experts warn that opening an executable file from an unknown source is a good way to download a Trojan or other unwanted program that can damage your computer and create a security risk.

The subject line in the greeting varies, from a generic hello to references to a specific holiday or event. Last week a number of these bogus E-Cards used the U.S. July 4 Independence Day celebration to lure victims into their trap.

Cyber criminals easily take advantage of celebrations like the 4th July to infect innocent people's computers, and potentially steal their identities. This is not just an American problem - these kinds of attacks strike around the world, and are designed to abuse PCs on a global scale, said Brett Myroff, CEO of NetXactics, a distributor of Sophos security software.

Sophos says those who fall for the ruse will be taken to a zombie computer, which attempts to load the virus. The virus then tries to download additional code from the Internet.

Security experts advise that people who receive a an unexpected E-Card from a person they do not know, or have not heard from for a long time, should delete it without opening it, as they would any other email from an unknown, or suspect, source.

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