Zlob Trojans are some of the most insidious Trojans out there.  If you’ve ever tried to watch video from a web site, only to be informed you needed to download a special “codec”, then you’ve probably run into a Zlob Trojan.  They are insidious.

They’re even worse because they do a really good job of pretending like they are legitimate software.  They’ll often have fake end-user license agreements to that they’ll seem like the real deal.  But really, these are just there to fool the unsuspecting user into downloading malicious software.

Sometimes the agreement will tell you exactly what you’re about to download, but in the kind of shifty language where you can’t really know the maliciousness of what you’re downloading is.

Once you’ve downloaded this software, you’ll start to see lots of adware.  You’ll get screens taking over your desktop, posing as security warnings.  You’ll probably even have pop-up windows telling you your system is infected.  (“ActiveX Object Error” is one common message that comes up.)

Of course, you’ll be instructed to buy a specific kind of “anti-spyware”, or at least run a check with it, in order to “fix” your computer.

But this is far from the end of things.  Zlob Trojans keep on downloading adware and rogue anti-spyware.  You’ll just get more and more “error–run scan with X software” messages.  And they’ll look more and more legitimate–much of this kind of malicious adware and rogue anti-spyware is designed to look either like a Windows security alert, or else like a real and legitimate anti-spyware program.

Zlob Trojans uses the increasing popularity of internet video to make potential victims of us all.  This kind of malicious adware doesn’t just come from video sites.  Online greeting card sites, music download sites, and even instant messengers can transmit this kind of malicious software.

So what can you do to protect yourself?

Read any end-user license agreement you are shown.  The time you take may seem irritating, but it’s worth it.  Real agreements, while sometimes long, are easy to understand.  The agreements for this kind of malicious adware generally are not.

Verify what you’re downloading.  Before you download any kind of video codec (or any other executable file you’ve never heard of), make sure you know exactly what it is.  Google it, use an online virus scanner (or your own–you really should have at least one spyware checker).  Find a good security support forum and make sure it has a search function.

If even one of these sources says the file is questionable, you probably shouldn’t download.  If all three tell you that, you definitely want to keep it off your computer.

Use up to date spyware protection.  In today’s day and age, this is absolutely essential.  Make sure you’ve got an legitimate anti-spyware program (i.e. one that you chose–not one that downloaded itself and then expected you to buy the full version), update it daily, and use it!