Before we get to the detailed view of how this trojan works, we want the message to be very clear: This software is a fake. Do not be fooled by this scam. This malware can potentially cause consumers and small business owners harm. Microsoft Security Essentials can be downloaded and used at no cost by users running genuine Windows (Download here: http://www.microsoft.com/security_essentials/). So anything mimicking Microsoft Security Essentials but asking for any sort of payment is clearly up to no good.
If you have not already updated your security software please do so. Making sure your security software is up-to-date and has the latest definitions is the best way to prevent infections.
And now onto a detailed look at FakePAV. While different FakePAV distributions have different payloads, here is how the current one imitating Microsoft Security Essentials works:
1. It modifies the system so that it runs when Windows starts
2. When you go to execute something it’s watching for, it opens the alert window claiming the program is infected and blocks it from running.
3. You can expand it out for “additional details”
4. If you click “Clean computer” or “Apply actions”, it simulates an attempt to clean the claimed infection
5. You’ll then get an ‘unable to clean’ alert and be instructed to click ‘Scan Online’
6. Clicking this, a list of antimalware programs appears, including several fake removal tools, and you’d need to click Start Scan
7. Once the simulated scan completes, it will claim a solution was found and list products that can ‘clean’ the system (the listed products are fake removal tools).
8. Clicking ‘Free install’ on one of those downloads will download its installer and start installing
If you believe your machine has become infected, we encourage you to use Microsoft Security Essentials to check your PC for malware and to help remove them from your system. You can also find out how to get virus-related assistance at no charge from Microsoft here: http://www.microsoft.com/protect/support/default.mspx.
For more information on this FakePAV please visit our encyclopedia entry at http://www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=Rogue%3aWin32%2fFakePAV. It contains a lot of information that may help answer questions about this rogue.
And remember: Microsoft does not charge for Microsoft Security Essentials. You can find the legitimate version of Microsoft Security Essentials at http://www.microsoft.com/security_essentials.