Pierluigi Paganini May 26, 2015

McAfee discovered in the Deep Web a ransomware-construction kits that allow easy to build malware in just 3 steps, implementing an interesting model of sale.

In the criminal underground it is easy to find malware-construction kits that allow easy to build malicious code from existing templates and in same cases starting from legitimate applications. A new trend emerged from investigation by experts at McAfee is a sort of easy to use Ransomware builder, this family of malware is becoming even more popular in the criminal ecosystem and crooks are trying to capture this opportunity.

The ransomware-construction kits, dubbed Tox, is available online for free in the Dark Web since May 19. The onion address of the website that offer it is

toxicola7qwv37qj.onion

“We developed a virus which, once opened in a Windows OS, encrypts all the files. Once this process is completed, it displays a message asking to pay a ransom to a bitcoin address to unlock the files. ” states the presentation of Tox available on the home page.

A user interested in Tox can subscribe the service to create their own virus. The authors explain that it is quite easy to create a ransomware in a few simple steps:

• Decide the ransom amount.
• Enter your “cause.”
• Submit the captcha

The creators of Tox request a percentage of the amount paid as ransom by the victims, they ensure the anonymity of payments and malware transfer through Bitcoin and Tor network. The authors of Tox ensure that the detection rate for the viruses generated by the platform is very low.

“Once you have downloaded your virus, you have to infect people (yes, you can spam the same virus to more people). How? That’s your part. The most common practice to spam it as a mail attachment. If you decide to follow this method be sure to zip the file to prevent antivirus and antispam detection.” is reported on the official website.
“The most important part: the bitcoin paid by the victim will be credited to your account. We will just keep a 30% fee of the income, so if you specify a 100$ ransom, you will get 70$ and we’ll get 30$, isn’t this fair?”

The key feature for Tox are:

• Tox is free. You just have to register on the site.
• Tox is dependent on TOR and Bitcoin. That allows for some degree of anonymity.
• The malware works as advertised.
• Out of the gate, the standard of antimalware evasion is fairly high, meaning the malware’s targets would need additional controls in place (HIPS, whitelisting, sandboxing) to catch or prevent this.antimalware evasion is fairly high, meaning the malware’s targets would need additional controls in place (HIPS, whitelisting, sandboxing) to catch or prevent this.

The crime-as-a-service model implemented by Tox author is simple as effective, the malware builder generates an executable of about 2MB that is disguised as a .scr file.

Tox subscribers can distribute it as they prefer while the Tox hidden service will track any installation and related profit. Tox customers will receive their funds directly on the Bitcoin address they provided during the subscription phase.

“Upon execution, the malware encrypts the victims’ data and prompts them for the ransom, including the Bitcoin address for sending payment.” states McAfee.

The expert at McAfee explained that the malware appears to lack complexity and efficiency because the developer has left several identifying strings within the code.

“Tox-generated malware is compiled in MinGW and uses AES to encrypt client files via the Crypto++ library.  The Microsoft CryptoAPI is used for key generation.”

Tox virus first downloads the essential components to work, Curl and the TOR client.

The experts highlighted that many other threat actors will adopt this model of sale, they also expect that malware authors will improve evasion capabilities of their malicious agents and will use encryption to protect malware traffic.

Pierluigi Paganini

(Security Affairs –  Tox, ransomware)

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