A digitally signed version of the popular CryptoWall ransomware is distributed via five Alexa top-ranked websites in a widespread malvertising campaign. The threat actors behind the campaign exploited a Drive-by downloads tactic to deliver the CryptoWall malware. The attack was delivered via the Zedo ad network and originated from the following five Alexa Top-ranked domains. The VirusTotal detection rate for this variant of CryptoWall was zero, after further analysis and in time it was improved with further analysis it is still low, which makes this threat very insidious.”]
Source: https://securityaffairs.co/wordpress/28821/malware/malvertising-signed-cryptowall.html