A malware called "ransomware” has led to recent demands of ransom payments, after malicious code became embedded on the legitimate ads. The new trend has been seen with ads on trusted Websites such as Yahoo, AOL, Match.com and The Atlantic.

The security firm Proofpoint (News - Alert) said the new variant of CryptoWall was spread via the banner ads, and was first noticed about a month ago.

The latest trend may expose up to 3 million visitors a day to the malware, and it is leading to the cyberthieves collecting about $25,000 per day, the firm adds.

"The sites themselves were not compromised; rather, the advertising networks upon which they relied for dynamic content were inadvertently serving malware – which in turn, was not due to an explicit compromise of the networks; rather, it was due to the networks accepting ads from a malicious source without screening detection," Proofpoint explained in a blog post.

Earlier, CryptoWall was sent through email attachments and links associated with the Cutwail spam botnet.

As of earlier this month, more than 830,000 computer users globally were infected by the malware, according to data from Dell (News - Alert) SecureWorks. That represents a 25 percent jump from August, when there were 625,000 victims, The Register reported.

The ransomware was identified as CryptoWall 2.0. Engadget explains it “uses Adobe (News - Alert) Flash to exploit browser vulnerabilities, installing itself on the affected computer. It then sets about encrypting files on the users' hard drive, refusing access to said files until the victim pays for a decryption key.”

“Typically, the end-users face an escalating time deadline; failure to pay by the deadline results in their hard drives being permanently encrypted, thus rendered effectively useless, with all information inaccessible,” Proofpoint warns.

In addition, the payment comes to about $500, but the attackers want it in the Bitcoin digital currency. In fact, Proofpoint said one of the Bitcoin wallets used in an attack for five days collected some $9,350 in Bitcoins. Looking at the big picture, The Register (News - Alert) reported that $1,101,900 in ransom was paid between March and August 2014 to the CryptoWall cybercriminals. In the last three months, 205,000 more victims got caught in the malware with the total in ransom payments reaching to $1.4 million or possibly more, The Register adds.

Computer users in the United Kingdom are among the most frequent victims of the malware. The region has more than 40,000 users who were victimized by the CryptoWall infections, The Register said. Ransoms range from $200 to $2,000, with larger amounts for those who do not pay quickly.

In order to prevent the attack, Engadget recommends users ensure software is current with the latest security patches in place. The report also says newer browsers should be adjusted so they only open plugins, including Flash, when a user clicks on content. Such a precaution will “eliminate the risk of being infected by this particular attack,” Engadget adds.