A new variant of SpyEye malware allows cybercriminals to monitor potential bank fraud victims by hijacking their webcams and microphones, according to security researchers from antivirus vendor Kaspersky Lab.

SpyEye is a computer Trojan horse that specifically targets online banking users. Like its older cousin, Zeus, SpyEye is no longer being developed by its original author, but is still widely used by cybercriminals in their operations.

SpyEye's plug-in-based architecture allows third-party malware developers to extend its original functionality, Kaspersky Lab malware researcher Dmitry Tarakanov said in a blog post on Monday. This is exactly what happened with the new webcam and microphone spying feature, which is implemented as a SpyEye plug-in called flashcamcontrol.dll, Tarakanov said.

As suggested by the DLL's name, the malware accesses these two computer peripherals by leveraging Flash Player, which has webcam and microphone control functionality built in.

Under normal circumstances, users get prompted to manually allow websites to control their computers' webcam and microphone via Flash. However, the SpyEye plug-in silently whitelists a list of online banking websites by directly modifying Flash Player configuration files.

At first, the Kaspersky Lab researchers thought that this might be part of a scheme to bypass facial recognition systems used by some banks for secure authentication. However, after contacting the targeted organizations, they learned that none of them had any webcam-reliant features on their websites.

The Kaspersky researchers later found out, by analyzing a different SpyEye component, that the malware injects the webcam and microphone hijacking Flash content into the targeted online banking websites locally, when these sites are opened in a browser on the infected computers.

This is done by using an on-the-fly Web page manipulation technique that most banking malware, including SpyEye, also uses for displaying rogue messages and hiding legitimate content inside the browser.

Some banks require customers to confirm transactions initiated from their online accounts by typing secret codes sent to their mobile phones or generated by portable hardware tokens. Cybercriminals need these codes to steal money, so they commonly use social engineering to trick victims into exposing them.

In other cases, the banks will actually call their customers in order to authorize transactions over the phone and this is when having webcam and microphone spying abilities can be very useful to attackers. Such was the case with an Ecuadorian bank whose customers were targeted in the past by a different piece of malware that had this functionality, Tarakanov said.

During conversations with the bank's phone operators, customers can disclose very sensitive information about themselves and their accounts, for the purpose of verifying their identity. This information can include their mother's maiden name, their date of birth, their credit card and Social Security numbers, as well as their telephone personal identification number (TPIN), which is used for phone banking operations.

"Using a microphone, the intruder can listen in, and later the criminal can call the bank himself, masquerading as a client whose code he has eavesdropped," Tarakanov said. "With this code it becomes possible to update the phone and login details, taking full control of the victim's account."

On the other hand, by hijacking webcams, cybercriminals can monitor how victims react when they read the socially-engineered messages displayed by the malware on online banking websites.

Cybercriminals are never 100 percent sure about how effective their social engineering tricks will turn out to be, Tarakanov said via email. It is important for them to understand where and why their attacks fail, so they can tweak them for better results, he said.

It's also possible that some of the targeted users will follow best practices and call their banks to verify the authenticity of any suspicious-looking messages they encounter during online banking sessions.

When they do this, they probably need to authenticate over the phone -- a process which, as noted previously, exposes sensitive information that can be captured through the microphone.

This particular attack shows how cybercriminals are not only harvesting people's money, but also their emotions, Tarakanov said in the blog post.

In order to protect themselves from such attacks, users could cover up their webcams when they're not using them, but that's not as easy to do with microphones, Tarakanov said via email.

Both webcams and microphones can be disabled from the operating system, either manually or with the help of specialized software, but that would hardly be convenient, especially for people who regularly use these peripherals.

It's much easier to prevent the infection in the first place by following basic security best practices like keeping all computer software up to date, running an up-to-date antivirus program, scrutinizing links before clicking on them and avoiding installing programs from suspicious sources, Tarakanov said.