Cryptowall 3 ransomware is the latest incarnation of the Trojan that first appeared in the latter half of 2014. This variant was discovered earlier this year and it has been used to extort millions out of individuals and businesses.

The threat from ransomware is growing

Ransomware infections have been reported much more frequently in recent months. A fortune has already been spent undoing the damage caused. Unfortunately, since the malware is evolving, it can be difficult to block.

Cryptowall 3 ransomware is very similar to previous incarnations and operates in a very similar fashion. The problem is that the algorithm it uses to obfuscate the dropper, which is applied three times, differs from Cryptowall 2. This makes it harder to identify.

Cryptowall 3 ransomware employs multiple dropper files and contains a number of different exploits. Once initiated, code is injected into a new explorer.exe process which installs the malware while disabling system protections. Malicious code is then hidden in a new SVChost.exe process.

The malware collects a considerable amount of data from the host computer, obtains an external IP address, establishes a connection, and registers the machine with the hacker’s command and control center. A POST request is made and the main Cryptowall 3 thread is initiated.

Cryptowall 3 ransomware subsequently encrypts certain file types on mounted network drives and local drives using public-key cryptography. The key to unlock the encryption is only stored on the hacker’s server. The victim is then advised to pay a ransom to have the infection removed and files unlocked. Failure to respond will see files locked forever or permanently deleted.

Cryptowall 3 ransomware is spread via email spam

Cryptowall 3 ransomware is primarily, but not exclusively, spread via spam email. The email contains a zip file attachment which houses an executable file. If the executable file is run, it installs the malware on the host computer. Videos, text files, and images files are then encrypted with its RSA2048 algorithm. Users often have files created on the desktop instructing them how to unencrypt their computer. Once infected, users are given approximately 7 days to pay the ransom, which is commonly $500 in the form of Bitcoins (2.17).

There is no guarantee that payment will result in the encryption being removed, although oftentimes it is. Payment certainly does not mean all traces of the malware will be removed from the infected machine. Users are often allowed to decrypt certain files to prove that the criminals behind the campaign can actually make good on their promise.

Victims are usually given little alternative but to give into the hacker’s demands, unless they want to lose all the files that have been encrypted.

Millions have been obtained from Cryptowall 3 ransomware infections

Cryptowall 3 ransomware has spread rapidly and the malware has already claimed tens of thousands of victims. The malware was only discovered in January 2015, yet already the criminals behind the infections have managed to obtain an estimated $325 million in ransoms according to Cyber Threat Alliance (CTA) figures. The ransoms have been tracked via Bitcoin payments, although the system used to assess criminals’ profits is somewhat unreliable. The figure of $325 million has been confirmed, but the total profits from Cryptowall 3 ransomware infections could well be double that total.

Cryptowall 3 ransomware infections usually start with a phishing campaign. The phishing campaigns usually contain an attachment with an innocent looking name, such as “invoice” or “fax”.

Drive-by attacks have been known to install the malware. These take advantage of security vulnerabilities in browser plugins. Exploit kits such as Angler are also used.

Fortunately, it is possible to train employees to be more cautious and not to open file attachments sent from unknown individuals. However, the emails may appear to have been sent by a friend, relative, or colleague inside their company.

Training should be provided to employees and company-wide warnings issued. However, the best defense is to prevent the ransomware from being delivered to inboxes. If SpamTitan Anti-Spam solutions are implemented, Cryptowall 3 ransomware email spam will be blocked and quarantined. End users will then be prevented from accidentally installing the malware.