The popup "Security Defender Firewall Alert!" or "Threat Detected Security Alert!" would strike fear into even the most seasoned of computer users.
But this malware popup alert is a FAKE -- a scam designed to get you to buy anti-virus software to remove a non-existent problem with a screen saying "Security Defender Firewall Alert" and displaying the program you are trying to open.
It gives you two options -- "Activate" (to register your copy of Security Defender) or "Stay Unprotected".
Also known as "scareware," this is a scam to get money from you, and does not provide virus or malware protection, but often renders your computer unusable. Once installed on your computer, this infection is considered a rogue anti-spyware program because it displays fake scan results, false security alerts, hijacks your web browser, and does not allow you to run your legitimate Windows applications.
The malware is downloaded from hacked web sites that attempt to install the software by exploiting vulnerabilities on your computer. It can also be installed through Trojan viruses that pretend to be legitimate programs, but will install the infection instead instead of virus removal software when you run them.
The malware is difficult to remove and will likely bring your computer to a complete halt with continuous pop-up messages and offers to fix the problem.
DO NOT click on the offers, they will not work, of course, there is no virus, so you pay for unnecessary service. The offer may also install mock antivirus software that later starts "finding" nonexistent malware. Worse, software may be installed that scans your computer to steal your passwords and hijack your computer to generate ads and spread spam.
Consult an expert or use a program such as MalwareBytes to remove the malware.
One of many variations of the Security Defender virus / malware popup screens. This warning is a fake, but the malware on your computer that causes it is very annoying and very real.
Another variation of a pop up warning from the malware Security Defender.
Security Defender is a scam.
Rogue security software might also attempt to spoof the Microsoft security update process. Here's an example of rogue security software that's disguised as a Microsoft alert but that doesn't come from Microsoft.