Saturday, April 13, 2024

Spammers Hide Trojan in Opt-Out Link

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Hackers are using a new ruse to trick users, rigging the opt-out link in

spam to download a hidden executable and turn the PC into an open proxy.

Once users click on the opt-out hyper link, they are taken to a

malicious Web page. If users pass their curser over a scroll bar, an

.exe file is downloaded onto their machine, making it available to

remote control, according to Natasha Staley, an information security

analyst with MessageLabs, Inc., a managed email security firm based in

New York. Staley says they have not found a high number of these emails

in circulation, but they are concerned that this is the very beginning

of a new trend in online assaults.

”Now that we’ve seen it once, the likelihood is that we’ll be seeing it

again,” says Staley, who adds that this is a potentially highly

dangerous attack method. ”When it’s something as apparently innocent as

running your [curser] over the scroll bar, how do you defend against

that? There’s nothing there to set your alarm bells ringing.”

What gives this new form of social engineering a boost is the fact that

the U.S. government passed the Can-Spam Act, which calls for all spam to

contain an opt-out link within the message. The government mandate adds

a sense of credibilty to this new opt-out ruse. Users might think that

since the law calls for the link to be included in the message, clicking

on it could stop the ever-increasing flow of spam into their in-boxes.

Generally, clicking on an opt-out link simply tells the spammer that

they’ve stumbled upon a working address, which they can then continue

using or even sell it to other spammers. Now clicking on the link could

make the machine part of a spammer’s army of zombie computers, ready to

send out millions of pieces of spam, launch denial-of-service attacks,

or offer up critical personal information on the PCs owner.

”The government asked spammers to put in an opt-out link, and that

could well be the reason why these spammers chose to do this,” says

Staley. ”They think people are more likely to trust opt-out links

because the government got involved with it. Now it’s a gray area and

users aren’t sure if they should click on it or if they shouldn’t.

”Ask yourself if you trust this spammer,” she adds. ”Do you really

believe they’ll take your email address off their list anyway? The

answer to that is generally no… Do not click on the opt-out link. Just

delete the email.”

This new ruse takes advantage of a flaw in Microsoft Corp.’s Internet

Explorer. The Drag-and-Drop JavaScript exploit uses the bug to download

the malicious code when the user’s curser passes over the scroll bar on

the Web page.

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