Fasten your seatbelts, for today we take you on a tour of fake-alert Trojans that have been doing rounds in the Internet lately. On this tour of various malware stations you’ll be taken to a system infected by a fake/rogue anti-virus application. Below is an example of a method implemented by such malware to infect a machine.

Here is your itinerary:

Station 1: Malicious web page that hosts a malware
Station 2: Browser helper object
Station 3: Fake/rogue anti-virus application downloader
Destination: Fake/rogue anti-virus application–infected system

The journey starts with a malicious web page that hosts a malware. Users reach these malicious pages through social engineering techniques such as a link via email/instant messanger, or redirection from a compromised legitimate website. A single click on these links will start the infection.

Upon visiting the malware-hosting web page, the user “buys a ticket” in the form of an executable file downloaded onto the system through some social engineering technique.

On our example tour,

• http://best[blocked]tube.net

When users visit the page above, they’re asked to download wmcodec_update.exe, which pretends to be a codec plug-in for Windows Media Player. A message box pops up repeatedly until users download the fake plug-in file, which is a Multi Dropper malware.

Upon execution, the downloaded file pops up a fake error message, as shown below:

The malware continues to execute and drops

1. Browser helper objects
2. Fake/rogue anti-virus application downloader

Our “tourists” now move to the next station, the browser helper object. At this station, the victims’ browsers are compromised. For example, a user’s search queries are manipulated to contain a link to another malicious web page. The following two images show the difference between a “clean” search and one made after a link to a malicious web page has been injected by the browser helper object. I have highlighted one malicious site; try to find five differences between the two images.

Before injection of the URL:

A compromised browser–after injection of the malicious URL:

Many spyware applications use browser helper objects to capture the surfing habits of users. This information is used later by the malware authors for pop-up ads relevant to search keywords, for example.

The next station on our tour is the fake/rogue anti-virus application downloader. Here users see two magazines, which are links to porn sites, on the desktop.

The fake application is downloaded without user intervention by the “fake” downloader. Finally the users systems are infected with a fake application malware.

At this point, users see a bogus alert from the fake application.

Scanning through the report generated by the fake app reveals that this report is exaggerated and false.

The fake-alert malware displays spurious alerts to entice users into buying products to “repair” the system from the fake, exaggerated threat.

Did you enjoy your fake-alert tour? Today, malware often work as a team to infect computers. In this tour, we saw a malicious web page hosting malware, Multi Dropper, a browser helper object, a downloader, and a fake alert work together for a common goal.

As always, we advise you to take precautions with fake plug-in downloads that loop infinitely–without giving you a chance to close that message box. Try to kill such processes of spurious messages through the Task Manager. Be careful about the links in your email, especially in anonymous mail and links in instant messages. Always practice “safe surfing,” which is the first step in keeping your computers clean.