Free Scan by Rogue Programs is Dangerous
Scareware or rogue and fake antivirus programs are dangerous because they not only infect the computer and cause performance issues, but also provide privacy risks to victims who provided their credit card information, name and e-mail address to the scammers in order to register the program.
If you are victim of the scammers that distributes rogue programs like fake AV scanners, immediately contact the credit card issuer by canceling the transaction for the said order of rogue program. You also need to request to the bank to replace your credit card.
You can prevent becoming a victim of scareware programs and scammers by not clicking on ads or opening strange email attachments which will install Trojans and provide fake alerts by the rogue scanner. Do not buy or register any software from untrusted sources and do not reveal your credit card and other valuable information to unknown people, websites or services, especially in websites of the fake antispyware programs. Anything security software that tries to force you into paying for something is most likely a scam.
It's recommended to have an extra layer of protection using trusted antivirus programs, a firewall that monitors outbound traffic, a host file such as MVPS or hpHOSTS, a browser security add-on such as Web of Trust or SiteAdvisor and by installing the updates for Windows and other applications.
Image Credit: Screenshot taken by the author.