By Leo Notenboom
I went to a website and the moment I got there, my computer started to tell
me that I had virus. I know I did not except for this advertising; I have
antivirus and antispyware and it still got in. I found it and put the program in the
all users application data. After I removed it and restored to an earlier date, it
was gone. I went back to the same site and nothing happened. So, my question is how
did it install the program on my computer and why did it not do it the second time
I went back to the same site?
First, I want to let you know that you were lucky; this approach to malicious
infection is incredibly devious and, sadly, often successful.
I also want to say that if you restored from a backup to get rid of it,
that’s excellent. Unfortunately, other manual approaches to getting rid of
malware – including system restore – are not guaranteed to always remove all
Let’s review what probably happened.
It’s A Trap!
It’s pretty easy to make something that looks like a very
legitimate Windows alert or error message that tells you “OMG! YOU’RE INFECTED!
CLICK OK TO FIX IT!”.
(I’ve used a very simple example – actual malware often replicates
very complex and official looking alert dialogs and message boxes.)
Of course, if you click on OK rather than dismissing the warning, the fake
message box is crafted to take that as a request to download and install
malware. In fact, a fake message box can be crafted so that anything that you might
do to close it, including clicking the “x” at the upper right or typing ALT+F4 to exit, actually instructs your browser to download and install malware.
Various approaches, including limited user accounts, or Windows User
Account Control, can help thwart the attempt or minimize the damage, but on
systems where security is lax, this is one way that malware purveyors get on to
A very common type of malware that does this is often referred to as
“hostage-ware”, because once installed, it demands payment to download software
that will supposedly remove the malware.
Don’t. Not only will you have given your credit card information to one of
the bad guys, but often, the “fix” simply doesn’t.
This post is excerpted with Leo’s permission from his blog.
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