Cryptowall 4.0 – the newest version of the world's worst Ransomware – has surfaced in the Nuclear exploit kit, one of the most potent exploit kits available in the underground market for hacking into computers.

Ransomware threat has emerged as one of the biggest threats to internet users in recent times. Typically, a Ransomware malware encrypts all files on victim’s computer with a strong cryptographic algorithm, then demand a ransom to be paid in Bitcoin. Cryptowall is currently among the most widespread and sophisticated family of Ransomware backed by a very robust back-end infrastructure.

BleepingComputer.com's editor Lawrence Abrams is reporting that a new version of the Cryptowall ransomware has been released, and has released details of why it's more of a threat than ever before.

Reporting on a new strain of Cryptowall, the ransomware trojan, BleepingComputer.com's editor Lawrence Abrams has reported on why the new version is more powerful than before and poses a security threat that at present has no resolution. Abrams became aware of the new Cryptowall variant when looking into cases where people reported they had been infected. He quickly determined that this was in fact a new version of CryptoWall.

A new spam wave has hit hundreds of mailboxes with malicious .chm attachments to spread the infamous Cryptowall ransomware.

Cryptowall is an advanced version of Cryptolocker, a file-encrypting ransomware known for disguising its viral payload as a non-threatening application or file. Its payload encrypts the files of infected computers in an effort to extract money for the decryption key. Malware researchers found that the email blast, which took place in February, targeted users from around the world, including the UK, the US, the Netherlands, Denmark, Sweden, Slovakia and Australia.

A sophisticated cyber-crime campaign is leaving millions of people vulnerable to having malware installed on their computers simply by visiting high profile websites.

The campaign is using the fast-growing method of 'malvertising' to spread a pernicious form of malware called ransomware, which encrypts all the files on the hard drive of a victim's computer, and if the victim doesn't pay a ransom by deadline, those files are lost forever. The researchers were even able to estimate how much money the criminals were earning on a daily basis as the ransoms are charged in bitcoin, meaning all payments are traceable via the public blockchain.

Victims of the CryptoWall ransomware have been extorted out of at least $1m. Despite a takedown operation in June, CryptoWall continues to be the largest and most destructive ransomware threat on the internet, according to the latest analysis of the threat by security researchers from Dell SecureWorks Counter Threat Unit.

Cryptowall is a strain of file-encrypting ransomware that encrypts files on infected Windows PCs and attached storage devices with RSA-2048 encryption before demanding a ransom for the private key that recovers the documents. Dell SecureWorks CTU researchers registered a domain used by the CryptoWall malware as a backup command and control (C2) server in February.