Update on the Torrentlocker ransomware

This posting is an update to the Torrentlocker blog posting of October 15. For guidance on containment and recovery, see the previous blog post.

Financial aspects

Payments for the ransom have to be done in Bitcoins. We have identified 7 Bitcoin addresses that received ransom payments. The total income as of the 21th of October is 862,79539531 BTC which comes down to 257.393,45 EURO made in payments to the criminals. Based on the current BTC price for the ransom, currently 1.32 BTC about 400 EURO, we can say that at least 653 victims have paid the ransom. We have confirmed 4180 infected clients up until October 21st. If they would all pay the ransom that would amount to 1.6 million euros.

Harvesting new e-mail addresses

Torrentlocker is currently being spread via phishing emails luring victims to fake postal service websites. One of the ways the criminals are getting new emails to send the emails towards is by harvesting email addresses from infected machines. It is able to grab email addresses from:

  • Thunderbird
  • Outlook
  • Windows Live Mail

We’ve found that they were able to harvest 2.614.109 email addresses in total. In addition to email addresses to use as a recipient, Torrentlocker also looks for IMAP/POP3/SMTP credentials to send the emails from. Started from the 20th we have seen them harvest a total of 1746 SMTP account credentials.


Location and number of the affected clients

This Torrentlocker campaign started on the 16th of September 2014 and has been targeting various countries. The criminals have made payment templates for the following countries:

  • Australia
  • Canada
  • Spain
  • Great Britain
  • Ireland
  • Italy
  • Namibia
  • Netherlands
  • New Zealand

They have been sending the phishing mails to recipients in the following countries:

  • Albania
  • Australia
  • Austria
  • Belgium
  • Canada
  • Chile
  • Colombia
  • Egypt
  • France
  • Germany
  • Great Britain
  • Greece
  • Hongkong
  • Hungary
  • India
  • Indonesia
  • Iran
  • Ireland
  • Isle of Man
  • Italy
  • Japan
  • Korea
  • Malta
  • Namibia
  • Netherlands
  • New Caledonia
  • New Zealand
  • Norway
  • Papue new Guinea
  • Philippines
  • Poland
  • Portugal
  • Puerto Rico
  • Qatar
  • Romania
  • Russia
  • Serbia
  • Singapore
  • South Africa
  • Spain
  • Sweden
  • Switserland
  • Turkey
  • United Arab Emirates
  • United States

In total we were able to confirm 4180 infections in 44 countries. This campaign first started on the 16th of September. They have done runs sometimes a week apart and sometimes only a day apart. The last run we saw started on the 21st of October. In every country they impersonate emails from the local postal service.

New IoCs

The following new domain names were used for hosting the fake website for the Dutch phishing campaign

  • Postnl-track.org
  • Postnl-track.net
  • Postnl-tracktrace.net

The following IP-addresses were additionally used for global C&C traffic


On the infected client system, the ransomware copies itself to a location based on whether it has admin privileges:

  • With admin privileges it will copy itself to C:\WINDOWS\[a-z]{8}.exe
  • Without admin privileges it will copy itself to C:\ProgramData\[a-z]{8}.exe

Additionally a startup key is added to the registry to start the ransomware upon a reboot.

New Torrentlocker variant active in the Netherlands


The Netherlands was hit with a new spam run designed to spread a cryptolocker variant known as torrentlocker from Monday October 13th 2014 onwards. Please note that torrentlocker appears to present itself to victims as cryptolocker in all cases. Fox-IT now receives multiple reports of new victims in the Netherlands and we are currently analyzing the new spam run and malware that was subsequently used.

This blogpost is aimed at providing victims with advice on how to deal with the infections. It contains technical details that will help system administrators trace back the original infection, and contain the spread of the infection as much as possible. We will update this blog post as more information is available.

What to do if you are a victim of torrentlocker?

You have fallen victim to torrentlocker if you find that a number of your (data) files have been encrypted and are unreadable. In this instance of torrentlocker, each directory that contains encrypted files will also contain an HTML-file with instruction on how to contact and pay the criminals behind this latest wave of torrentlocker attacks.

There are a number of things that you can do yourself to find the original infection and contain the spread of torrentlocker, and possibly restore files to their original state.

  1. Block access to certain resources on the internet in order to minimize the risk of further infections. For information on which resources to block, see section “Indicators of compromise in network traffic”.
  2. Activate system policies that prevent further activity by torrentlocker:
    1. Restrict “delete” permissions. Activate a policy that prevents users from deleting files from shares. We have indications that such a policy may prevent torrentlocker from working effectively. We are currently investigating this claim.
    2. Restrict “write” permissions. To be extra careful, you may change user’s rights on all files to “read-only”. This will prevent any changes to files.
  3. Identify the systems that are infected with torrentlocker. The following steps will help with identification:
    1. Identify who received emails as part of the spam run. In your email messaging logs, search for email messages with characteristics as described in the section “Indicators of compromise in email”. Any hits should provide you with information about who within your organization received emails as part of the spam run and will allow you to remove these emails.
    2. Identify who visited suspicious torrentlocker websites. In your gateway logs (proxy logs, firewall logs, IDS logs etc), search for visits to websites known to be associated with this spam run. Any hits should provide you with evidence which systems within your infrastructure visited those websites and are potentially infected with torrentlocker. More information about what to look for can be found in section “Indicators of compromise in network traffic”.
    3. Identify which systems are infected. After the previous two steps, you may have narrowed down the number of systems that are potentially infected and have caused the files to be encrypted. On suspected systems, you may use the information in the section “Indicators of compromise on hosts”.
  4. Isolate the infected systems from your infrastructure. Once identified, these systems should be carefully isolated from the infrastructure, to prevent further encryption of additional files but at the same time preserve digital traces.
    1. Immediately cease all user activity on infected systems as they may contain important clues for decryption of the encrypted files or additional information about the infection.
    2. Physically disconnect the infected systems from the network.
    3. Do not power off, wipe or reimage infected systems.
  5. Restore backups of the infected files. In case backups are not available or only partly available, and you have preserved sufficient digital evidence, you may seek professional assistance in an effort to recover infected files.

Infection process


Indicators of compromise in email

Within your messaging logs, you may search for emails with the subject:

Heb je niet geleverde packet

Starting on Sunday emails were sent around impersonating a Dutch postal company called PostNL. The emails were styled so as to look exactly like the company’s normal email communication:

postnl phishing

The recipient of the email is enticed to click on the ‘Zie de informatie’ link. This took the recipient to a compromised wordpress website used as redirection page towards the actual malicous page.

Indicators of compromise in network traffic

Within your gateway logs (proxy, firewall and IDS logs, etc) you may search for traffic to the following site in order to identify systems within your infrastructure that visited malicious websites associated with this attack. Please note that this list contains currently known resources on the internet but is not necessarily complete.

Initial websites linked to in the email:


The above websites redirected to:


Domains for command and control traffic over SSL:


Command and control IP’s involved with this threat:

Fake PostNL IP’s involved with this threat:

The domain ‘postnl-track.com’ had its CSS and images loaded from ‘postnl-track.com’. The page was a convincing page talking about a track and trace document being available:


The user is forced to enter the captcha in order to proceed. After the captcha the user is presented with a download of their track and trace information:


The user is presented with a zip which has the payload inside. After opening their ‘document’ the malware will start connecting with its command and control server, generate encryption keys and start encrypting files. After its completed the user is presented with the following notice:


When visiting one of the links of their payment website the user is told to pay 400 EURO’s within a certain time otherwise the price will be doubled:


Indicators of compromise on hosts

On suspected systems, you may look for the following clues of infection by torrentlocker. Please note that once you determine that a system is infected, you should remove it from your infrastructure. Do not wipe or reinstall the system as it may contain additional clues about the infection.

  • The initial infection is dropped as the following file C:\WINDOWS\[a-z]{8}.exe
  • There will be a reference in the registry to the previous file, to make sure that torrentlocker starts up automatically upon boot. You may use the Windows tool msconfig to inspect startup entries.
  • A second process “explorer.exe” will be active.

Update on DecryptCryptoLocker

A month ago Fox-IT and FireEye announced the DecryptCryptoLocker service, which provides free private keys to victims of the CryptoLocker Malware. We decided not only to share the information with victims for free, but also provide a website that provides the right key to victims, saving them a lot of time and effort. For each request the website needs to do comparisons to over half a million private keys to obtain the right one. This blog and the accompanying one from FireEye serves as an update on CryptoLocker and the DecryptCryptoLocker service.


We’ve got a lot of reactions, hundreds of inquiries and thank you notes, and tens of thousands of social media interactions. Steve Belleguelle, system administrator for multiple customers, wrote “Just a short message to say thank you so much for the work in obtaining the CryptoLocker keys database and then providing the DecryptCryptoLocker website. One of my customers ‘lost’ many thousands of files due to this malware and we have now been able to recover most of them.” For us that reaction alone makes it worth the effort, but Steve is not alone: up until last week we were able to provide 2900 keys to victims, and dozens of keys are still being provided on a daily basis. For that reason we decided to keep the DecryptCryptoLocker website running for several months. If you know a victim, point them to it.

Update on CryptoLocker

Most of the operators behind P2P ZeuS and CryptoLocker have not been seen since the operation against this group and their infrastructure, however this does not mean that the threat has gone away. The past months have seen a lot of fluidity, caused by new players trying to enter this space and existing customers of the P2P ZeuS group looking for new solutions for their crimeware needs.

Parts of the inject code have reappeared in other botnets, we are tracking new malware variants being developed which appear to re-use or build upon parts of P2P Zeus and there is an upsurge activity from Gozi, Bugat and other existing malware variants. This means some of the high profile customers of P2P Zeus are looking for a new custom piece of malware while others customers simply joined other existing operations like Gozi.

The fact that the CryptoLocker malware netted the P2P Zeus group significant income has also lead to renewed interest in ransomware as a way to make money and copycat malware using the same approach have now appeared, an example being Cryptowall – which has even copied part of the name.

Some numbers

When we started the project, we could only guess how many people we would be able to help. Now, after a month we can do a first assessment.

Please note that these statistics are not in any way correlated to personal identifiable information; and that PII was used for nothing else than delivering the private keys.

The infection rate as mentioned in the original blog post is shown below:


If we compare that to the decryption requests, we can see the data correlates. Indeed the top countries requests are made from, are countries where English is a major language.



The total number of valid decryption requests is 2900. An interesting fact is that in the UK, relatively more victims have requested their keys than in the US – more than in all other large countries to be precise. Only some very small countries with a handful of infections showed greater ratios, which can be attributed to too low statistical sample sizes.

The type of files that were offered for private key matching show some interesting things too.


Although this is not necessarily a representation of the actual files being encrypted with malware, one can imagine that a .dwg file (a CAD file) might represent a lot of value to the victim, in terms of specialist hours spent on working on the file.

Feedback and other ransomware victim solutions

We try to answer every question we’re asked via e-mail or social media. Due to the overwhelming amount of feedback a reaction might have taken some time. The most asked question was from victims of other ransomware: will we be able to provide a solution for CryptoWall, Synolocker, CryptoLocker V2 or others? Unfortunately we don’t offer decryption keys for these ransomwares. It is unlikely we will provide something for that anytime soon.


The DecryptCryptoLocker service has been able to help thousands, and will be continued for several months, hopefully helping more victims reclaiming their files. While the original CryptoLocker malware is not used anymore, criminals though seem encouraged by its success and many more families of ransomware are now seen in the wild.

CryptoLocker ransomware intelligence report

In the beginning of September 2013, the CryptoLocker malware variant appeared in the wild, spread exclusively by the infamous P2P ZeuS (aka Gameover ZeuS) malware. CryptoLocker had a simple purpose: to act as ransomware, encrypting important files such as images and documents, and then asking the victim for money to unlock the files.

CryptoLocker warning
Image source: Ars Technica

In collaboration with FireEye, InTELL analysts at Fox-IT worked on the investigation. By the end of 2013, certain groups that were focused on online banking fraud, were moving to less risky attacks, such as ransomware, click fraud, and crypto coin mining. All of these attack types pose lower risk to the criminals compared to online banking attacks. P2P ZeuS was one of these groups.

US Law Enforcement led a joint operation from the 30th of May 2014, leading to a long term disruption of both P2P Zeus and CryptoLocker. A detailed description of the operation is available here.

CryptoLocker used AES symmetric cryptography to encrypt the files and encrypted the AES key with an RSA-2048 bit public key generated on the server side of CryptoLocker. For each infection a new RSA asymmetric key pair was generated on the CryptoLocker server. This rendered files impossible to recover for CryptoLocker victims on their own. To recover files, the malware offered victims the option to purchase the required RSA-2048 private key. The CryptoLocker authors began charging victims 100 USD in September 2013 to recover their files, and by May 2014, were charging victims 500 USD for recovery.

Not every computer infected with P2P ZeuS malware became infected with CryptoLocker. The reason for this is that CryptoLocker ran on victim machines alongside P2P ZeuS malware, which was used to commit financial fraud. In order for P2P ZeuS to be successful, a victim had to remain unaware that his/her system was compromised. Therefore, only a handful of P2P ZeuS botnets within the full P2P ZeuS network installed CryptoLocker. From September 2013 through May 2014, over half a million (545,146) infections occurred. This is much less than the amount of infections of P2P ZeuS over the same period.

Of the botnets distributing CryptoLocker, infections were mostly limited to victims located in the US, Canada, UK and Australia. These regions were most likely selected for their use of English as the primary language. This is shown in the heat map below – with over 60% of the CryptoLocker infections located in the US.


While CryptoLocker infections started in the beginning of September 2013, the largest number of infections in one month occurred during October 2013, with over 155000 systems affected worldwide. This accounts for nearly 29% of all infections between September and May 2014. After October 2013 the rates dropped, but still steadily pacing at around 50,000 infections per month.

The CryptoLocker infrastructure was separate from the P2P ZeuS infrastructure. It used a fast-flux network offered by a bulletproof hoster and a service hidden in the TOR network. These two channels were terminated on a proxy system that lead directly to the backend system, allowing victims to pay the ransom even though the fast flux network experienced various disruptions by security researchers.

The majority of victim payments to CryptoLocker were processed through Moneypak, but also a considerable amount of money was paid through the use of Bitcoins. A new Bitcoin address was created for each infection, making it harder for researchers to track and easier for CryptoLocker operators to distinguish transactions. In total, over 1400 Bitcoins (1407.24575477 BTC, around 700,000 USD in current exchange rates) were received. That is more than the 1388 BTC the malware requested, apparently some victims tried to transfer partial amounts. Unfortunately for them these lower amounts were lost for them and they added a small bonus for the criminals. A small number of early payments were received via Paysafecard and Ukash. In total, the amount of money made during the 9 month CryptoLocker operation was around 3 million USD. This accounts for the fluctuating Bitcoin exchange rate over time.

In the end, 1.3% of victims paid a CryptoLocker ransom, therefore, a large amount of victims likely permanently lost files due to this attack. Fox-IT InTELL and FireEye provide a free service to victims, to recover the private keys associated to CryptoLocker infections. This was announced on August 6 2014, in this press release. This gives CryptoLocker victims the ability to recover their files and restore the contents.

A big thank you to Kyrus tech for their tool Cryptounlocker. And finally we wish to thank Surfright for their assistance by providing encrypted files they generated using CryptoLocker.

Michael Sandee