14 ms·

Ransomware Decryptor

205 points by touristtam 12y ago

ronald_dregan 12y ago
neat
Animats 12y ago
Key distribution is a problem even for ransomware. It looks like the decryption key is a function of the Bitcoin address to which ransom is sent. That should eliminate the need for a server controlled by the ransomware people to return keys. What does "check payment and receive keys" really do? Does it check the Bitcoin block chain to see if payment has been made, then calculate the decryption key? Is this entirely blockchain-based?
- 3pt14159 12y ago
  I'm guessing that when a cyber criminal is caught they add all retrieved private keys to the police's keychain. Even a symmetrically signed key (passworded) can be brute forced or the arrested can be court compelled to decrypt the key.
  - duaneb 12y ago
    AES cannot be trivially brute forced. The key phrase is also unlikely to be trivial because the convenience has no value.
    - will_hughes 12y ago
      I don't understand, perhaps I'm misunderstanding the situation. GP is saying that if the [private] key is password protected, it can be brute forced. Surely if a human is able to type in the password to the private key, you can bute force that password relatively easily?
      - nitrogen 12y ago
        bute[sic] force that password relatively easily? "Easily" conceptually, yes, but not computationally.
      - duaneb 12y ago
        With cooperation, yes, without it, no. A password doesn't need to be too long to grow the key space to large enough all the computers in the world couldn't scratch the surface. Of course, there are many other factors that can significantly decrease or break the security of AES. TL;DR xkcd.com/538
- StavrosK 12y ago
  I'm not sure, I spent five minutes thinking about it, and it's pretty easy to come up with a design that relies on no servers, accepts payment through Bitcoin and the decryption keys are only ever stored with the operator and never divulged before payment. Maybe malware operators aren't that experienced, who knows.
  - ikeboy 12y ago
    I don't know about Coinvault, but other systems would generate the private key on a server and send the public key to the computer for encryption. I don't see how you could have zero servers and still send the private key upon payment, though. There was an early version that would generate the private key locally, which was discovered by Symantec (the original blog post isn't loading, but you can see it at https://archive.is/1AGHG https://archive.is/1AGHG) For an analysis of a more recent version that fixed this see http://www.secureworks.com/cyber-threat-intelligence/threats/cryptowall-ransomware/ http://www.secureworks.com/cyber-threat-intelligence/threats... A TorLocker had flaws that allowed 70% of infections to be recovered, see https://securelist.com/blog/research/69481/a-flawed-ransomware-encryptor/ https://securelist.com/blog/research/69481/a-flawed-ransomwa..., although they didn't explain what flaws there were.
- ikeboy 12y ago
  They have a captured database of key/Bitcoin addresses, so when you put in the address it looks up the key. >What does "check payment and receive keys" really do? Presumably it asks the server whether the payment was received, and if the answer is yes, the server sends it the key.
techwatching 12y ago
This originally hit the news 10 days ago: http://techwatching.com/page/there-s-finally-a-tool-to-free-you-from-the-ransomware-holding-your-pc-hostage http://techwatching.com/page/there-s-finally-a-tool-to-free-...
- touristtam 12y ago
  Yeah, somehow no one on HN upvoted the stories, previously posted, about it. And, for once, I am glad I didn't do my usual search before posting. Otherwise this is a tool that wouldn't have had much exposure among the HN crowd. But this is a different topic altogether. ;)
IgnotisAnon 12y ago
Keep in mind that this only works for people infected with CoinVault, and Kaspersky didn't get all the keys. The title is misleading here. Still, if you are infected by CoinVault or know somebody who is, this is a great thing to try.
theandrewbailey 12y ago
I would suspect that the keys would be different for each infection. But then considering this is software made by criminals, I would not expect even the most sensible or trivial of features and security precautions would be implemented.
- ge0rg 12y ago
  Implementing this right is surprisingly hard, as the Debian SSL fiasco and the Java/Android's so called SecureRandom RNG have shown. Maybe they were using a defective RNG for the keys as well, so in total there is a very limited number of keys out there, making collisions probable?
  - duskwuff 12y ago
    Or possibly they seized the C&C servers and recovered all of the encryption keys stored on them?
    - fragmede 12y ago
      That's exactly what happened. https://securelist.com/blog/69595/challenging-coinvault-its-time-to-free-those-files/ https://securelist.com/blog/69595/challenging-coinvault-its-...
- schoen 12y ago
  The ransomware developers could use public-key cryptography by generating a local session key to encrypt the victim's files, and then encrypting a copy of that key with the developers' public key. The paid ransomware service would then consist of decrypting that particular session key on request. Perhaps the ransomware developers don't understand this or thought it was too much work, or perhaps they want to provide a better user experience by sending a unilateral unlock code rather than requiring the victim to send any data to the attacker. Congratulations to the people behind this collaboration for making progress on helping the victims.
  - hurin 12y ago
lucb1e 12y ago
As a Dutch person, I was confused about the Dutch police logo there (Politie is Police in Dutch). Scrolled to the bottom to find affiliation or anything... turns out it's right there in the first line. I'm very pleasantly surprised to see our police doing something good! It's the first time I've heard the Dutch digital police actually achieving anything, and that is not exaggerated. Last time we provided an IP address involved in a hack (the IP was from the same town as the company that got hacked, so it wasn't masked), we never heard anything back, even though we know they have the CIOT database with all Dutch IP addresses mapping to names and addresses. But that was 2 years ago and there have been a lot of activities in training policemen for digital investigations. Although it's not entirely clear what exactly their involvement was, this is nice!
- thaumaturgy 12y ago
  That's not uncommon, unfortunately. I've off-and-on bothered to notify various entities about bad behavior for the last 15 years or so. In most cases, it goes completely ignored. Most recently, on April 2, I notified Rackspace's abuse department that they were hosting a major fraud/scam site (websitebackup.com, they send out fraudulent invoices and wait for non-tech-savvy customers to send payment) and never heard back. Rackspace is still hosting them. It's just one of those facts of life: nobody really cares, not until they're directly affected by it somehow.
  - lucb1e 12y ago
    Hold on, Rackspace is not police. You have no legal right to demand that they cease to host anything and they have no legal obligation to look into anything sent to that email address. The company that got hacked and reported it to the police did: someone violated the law, we provided IP addresses and access logs to make it a clear and simple case, and then they didn't even look into it.
    - thaumaturgy 12y ago
      Yes, and that's not uncommon, whether police or state agency or otherwise.
eugeneionesco 12y ago
>During our joint investigation we have been able to obtain data that can help you to decrypt the files being held hostage on your PC. Obtain data? How? :)
- ikeboy 12y ago
  http://www.pcworld.com/article/2909292/files-encrypted-by-coinvault-ransomware-new-free-tool-may-decrypt-them.html http://www.pcworld.com/article/2909292/files-encrypted-by-co... >The National High Tech Crime Unit (NHTCU) of the Dutch police recently obtained a database from a CoinVault command-and-control server containing decryption keys, the Dutch police said in a news release. The information obtained from that database allowed Kaspersky to build a decryption tool.
  - hnarn 12y ago
    >a CoinVault command-and-control server So, is there anything stopping them from setting up new servers with new keys and starting the goose chase all over again?
    - ikeboy 12y ago
      No. In fact, this already happened before, see https://www.decryptcryptolocker.com/ https://www.decryptcryptolocker.com/. It helps some people already infected.
mef 12y ago
In the manual[0] they have "Remove CoinVault" as a step to do before you check whether the Kaspersky site has the key that will decrypt your files. People probably want to keep CoinVault around in case the key isn't known and they want to pay the ransom. [0] https://noransom.kaspersky.com/static/convault-decrypt-manual.pdf https://noransom.kaspersky.com/static/convault-decrypt-manua...
- ikeboy 12y ago
  Don't know about Coinvault specifically, but others give you a program along with the key if you pay. Besides, you can always use Kaspersky's tool with a paid for key.
ikeboy 12y ago
For how they built it, see https://securelist.com/blog/69595/challenging-coinvault-its-time-to-free-those-files/ https://securelist.com/blog/69595/challenging-coinvault-its-...
- terminado 12y ago
  That link does not explain how they're managing to obtain the correct key from the server without paying money. So they were able to dump a memory segment into a hex editor, and locate references to RijndaelManaged. So what? In the screenshot, I still see: Server.GetKey().Key So how did they convince the malicious server to cough up the token for free?
  - sbisker 12y ago
    The article comments mention that you need to have the Bitcoin wallet address to use the tool to decrypt the files. Either they found some relationship between the wallet and the secret used for the encryption, or they actually compromised the servers and have a true mapping between every wallet address and the key subsequently used for that encryption.
  - ikeboy 12y ago
    The article says they were given the keys by the police.
  - fragmede 12y ago
    The article states they "...obtained a database from a CoinVault command & control server (containing IVs, Keys and private Bitcoin wallets)." Reading between the lines, the police located the server, served a subpoena to the hosting company, and took possession of the server. They then turned it over to Kaspersky who created the site based on the keys on that server. The screen dumps are just showing how they figured out the decryption routine - the private key alone doesn't do you much good if you don't know the algorithm used.
    - deleted 12y ago
      [deleted]
michaelmior 12y ago
The title appears to have a typo: ransomEware.
bbcbasic 12y ago
The best Ransomeware Decryptor is the backup you took last night. Which reminds me ... :-)
- hnarn 12y ago
  Why assume that no-one who ever got caught by ransomware had any backups? As far as I know, the way most ransomware works is that it not only encrypts your entire drive, but also any network drives it has access to, any external drives, and so on. It's quite possible someone with a backup regiment was still affected because they left a link to their backup system open, encrypting that as well. I think most people mainly care about backups being off-site, not them being "de-linked" and unaccessible.
  - seszett 12y ago
    > I think most people mainly care about backups being off-site, not them being "de-linked" and unaccessible. Then they don't understand backups - what's the use of backups if rm -rf / erases them as well because they're permanently mounted at /srv/backup?
  - leni536 12y ago
    This should remind you that a safe backup should be pulled from the backup server. Alternatively you keep an incremental backup on your server and give other computers limited privileges (they shouldn't have write access to snapshots).
  - GnarfGnarf 12y ago
    Do your backups to DVD and you're guaranteed ransomeware can't touch them.
  - bbcbasic 12y ago
    Good point. I would format any disk that has had ransomware on it before I did anything else (like plug in the usb drive with my backup). In the meantime use another PC to access the files. However yes it is probably worth having 2 backups for this reason, just incase you get caught short.

205 points by touristtam 12y ago

neat

Key distribution is a problem even for ransomware. It looks like the decryption key is a function of the Bitcoin address to which ransom is sent. That should eliminate the need for a server controlled by the ransomware people to return keys. What does "check payment and receive keys" really do? Does it check the Bitcoin block chain to see if payment has been made, then calculate the decryption key? Is this entirely blockchain-based?

3pt14159 12y ago
I'm guessing that when a cyber criminal is caught they add all retrieved private keys to the police's keychain. Even a symmetrically signed key (passworded) can be brute forced or the arrested can be court compelled to decrypt the key.
- duaneb 12y ago
  AES cannot be trivially brute forced. The key phrase is also unlikely to be trivial because the convenience has no value.
  - will_hughes 12y ago
    I don't understand, perhaps I'm misunderstanding the situation. GP is saying that if the [private] key is password protected, it can be brute forced. Surely if a human is able to type in the password to the private key, you can bute force that password relatively easily?
    - nitrogen 12y ago
      bute[sic] force that password relatively easily? "Easily" conceptually, yes, but not computationally.
    - duaneb 12y ago
      With cooperation, yes, without it, no. A password doesn't need to be too long to grow the key space to large enough all the computers in the world couldn't scratch the surface. Of course, there are many other factors that can significantly decrease or break the security of AES. TL;DR xkcd.com/538
StavrosK 12y ago
I'm not sure, I spent five minutes thinking about it, and it's pretty easy to come up with a design that relies on no servers, accepts payment through Bitcoin and the decryption keys are only ever stored with the operator and never divulged before payment. Maybe malware operators aren't that experienced, who knows.
- ikeboy 12y ago
  I don't know about Coinvault, but other systems would generate the private key on a server and send the public key to the computer for encryption. I don't see how you could have zero servers and still send the private key upon payment, though. There was an early version that would generate the private key locally, which was discovered by Symantec (the original blog post isn't loading, but you can see it at https://archive.is/1AGHG https://archive.is/1AGHG) For an analysis of a more recent version that fixed this see http://www.secureworks.com/cyber-threat-intelligence/threats/cryptowall-ransomware/ http://www.secureworks.com/cyber-threat-intelligence/threats... A TorLocker had flaws that allowed 70% of infections to be recovered, see https://securelist.com/blog/research/69481/a-flawed-ransomware-encryptor/ https://securelist.com/blog/research/69481/a-flawed-ransomwa..., although they didn't explain what flaws there were.
ikeboy 12y ago
They have a captured database of key/Bitcoin addresses, so when you put in the address it looks up the key. >What does "check payment and receive keys" really do? Presumably it asks the server whether the payment was received, and if the answer is yes, the server sends it the key.

techwatching 12y ago

This originally hit the news 10 days ago: http://techwatching.com/page/there-s-finally-a-tool-to-free-you-from-the-ransomware-holding-your-pc-hostage http://techwatching.com/page/there-s-finally-a-tool-to-free-...

touristtam 12y ago
Yeah, somehow no one on HN upvoted the stories, previously posted, about it. And, for once, I am glad I didn't do my usual search before posting. Otherwise this is a tool that wouldn't have had much exposure among the HN crowd. But this is a different topic altogether. ;)

IgnotisAnon 12y ago

Keep in mind that this only works for people infected with CoinVault, and Kaspersky didn't get all the keys. The title is misleading here. Still, if you are infected by CoinVault or know somebody who is, this is a great thing to try.

theandrewbailey 12y ago

I would suspect that the keys would be different for each infection. But then considering this is software made by criminals, I would not expect even the most sensible or trivial of features and security precautions would be implemented.

ge0rg 12y ago
Implementing this right is surprisingly hard, as the Debian SSL fiasco and the Java/Android's so called SecureRandom RNG have shown. Maybe they were using a defective RNG for the keys as well, so in total there is a very limited number of keys out there, making collisions probable?
- duskwuff 12y ago
  Or possibly they seized the C&C servers and recovered all of the encryption keys stored on them?
  - fragmede 12y ago
    That's exactly what happened. https://securelist.com/blog/69595/challenging-coinvault-its-time-to-free-those-files/ https://securelist.com/blog/69595/challenging-coinvault-its-...
schoen 12y ago
The ransomware developers could use public-key cryptography by generating a local session key to encrypt the victim's files, and then encrypting a copy of that key with the developers' public key. The paid ransomware service would then consist of decrypting that particular session key on request. Perhaps the ransomware developers don't understand this or thought it was too much work, or perhaps they want to provide a better user experience by sending a unilateral unlock code rather than requiring the victim to send any data to the attacker. Congratulations to the people behind this collaboration for making progress on helping the victims.
- hurin 12y ago

lucb1e 12y ago

As a Dutch person, I was confused about the Dutch police logo there (Politie is Police in Dutch). Scrolled to the bottom to find affiliation or anything... turns out it's right there in the first line. I'm very pleasantly surprised to see our police doing something good! It's the first time I've heard the Dutch digital police actually achieving anything, and that is not exaggerated. Last time we provided an IP address involved in a hack (the IP was from the same town as the company that got hacked, so it wasn't masked), we never heard anything back, even though we know they have the CIOT database with all Dutch IP addresses mapping to names and addresses. But that was 2 years ago and there have been a lot of activities in training policemen for digital investigations. Although it's not entirely clear what exactly their involvement was, this is nice!

thaumaturgy 12y ago
That's not uncommon, unfortunately. I've off-and-on bothered to notify various entities about bad behavior for the last 15 years or so. In most cases, it goes completely ignored. Most recently, on April 2, I notified Rackspace's abuse department that they were hosting a major fraud/scam site (websitebackup.com, they send out fraudulent invoices and wait for non-tech-savvy customers to send payment) and never heard back. Rackspace is still hosting them. It's just one of those facts of life: nobody really cares, not until they're directly affected by it somehow.
- lucb1e 12y ago
  Hold on, Rackspace is not police. You have no legal right to demand that they cease to host anything and they have no legal obligation to look into anything sent to that email address. The company that got hacked and reported it to the police did: someone violated the law, we provided IP addresses and access logs to make it a clear and simple case, and then they didn't even look into it.
  - thaumaturgy 12y ago
    Yes, and that's not uncommon, whether police or state agency or otherwise.

eugeneionesco 12y ago

>During our joint investigation we have been able to obtain data that can help you to decrypt the files being held hostage on your PC. Obtain data? How? :)

ikeboy 12y ago
http://www.pcworld.com/article/2909292/files-encrypted-by-coinvault-ransomware-new-free-tool-may-decrypt-them.html http://www.pcworld.com/article/2909292/files-encrypted-by-co... >The National High Tech Crime Unit (NHTCU) of the Dutch police recently obtained a database from a CoinVault command-and-control server containing decryption keys, the Dutch police said in a news release. The information obtained from that database allowed Kaspersky to build a decryption tool.
- hnarn 12y ago
  >a CoinVault command-and-control server So, is there anything stopping them from setting up new servers with new keys and starting the goose chase all over again?
  - ikeboy 12y ago
    No. In fact, this already happened before, see https://www.decryptcryptolocker.com/ https://www.decryptcryptolocker.com/. It helps some people already infected.

mef 12y ago

In the manual[0] they have "Remove CoinVault" as a step to do before you check whether the Kaspersky site has the key that will decrypt your files. People probably want to keep CoinVault around in case the key isn't known and they want to pay the ransom. [0] https://noransom.kaspersky.com/static/convault-decrypt-manual.pdf https://noransom.kaspersky.com/static/convault-decrypt-manua...

ikeboy 12y ago
Don't know about Coinvault specifically, but others give you a program along with the key if you pay. Besides, you can always use Kaspersky's tool with a paid for key.

ikeboy 12y ago

For how they built it, see https://securelist.com/blog/69595/challenging-coinvault-its-time-to-free-those-files/ https://securelist.com/blog/69595/challenging-coinvault-its-...

terminado 12y ago
That link does not explain how they're managing to obtain the correct key from the server without paying money. So they were able to dump a memory segment into a hex editor, and locate references to RijndaelManaged. So what? In the screenshot, I still see: Server.GetKey().Key So how did they convince the malicious server to cough up the token for free?
- sbisker 12y ago
  The article comments mention that you need to have the Bitcoin wallet address to use the tool to decrypt the files. Either they found some relationship between the wallet and the secret used for the encryption, or they actually compromised the servers and have a true mapping between every wallet address and the key subsequently used for that encryption.
- ikeboy 12y ago
  The article says they were given the keys by the police.
- fragmede 12y ago
  The article states they "...obtained a database from a CoinVault command & control server (containing IVs, Keys and private Bitcoin wallets)." Reading between the lines, the police located the server, served a subpoena to the hosting company, and took possession of the server. They then turned it over to Kaspersky who created the site based on the keys on that server. The screen dumps are just showing how they figured out the decryption routine - the private key alone doesn't do you much good if you don't know the algorithm used.
  - deleted 12y ago
    [deleted]

michaelmior 12y ago

The title appears to have a typo: ransomEware.

bbcbasic 12y ago

The best Ransomeware Decryptor is the backup you took last night. Which reminds me ... :-)

hnarn 12y ago
Why assume that no-one who ever got caught by ransomware had any backups? As far as I know, the way most ransomware works is that it not only encrypts your entire drive, but also any network drives it has access to, any external drives, and so on. It's quite possible someone with a backup regiment was still affected because they left a link to their backup system open, encrypting that as well. I think most people mainly care about backups being off-site, not them being "de-linked" and unaccessible.
- seszett 12y ago
  > I think most people mainly care about backups being off-site, not them being "de-linked" and unaccessible. Then they don't understand backups - what's the use of backups if rm -rf / erases them as well because they're permanently mounted at /srv/backup?
- leni536 12y ago
  This should remind you that a safe backup should be pulled from the backup server. Alternatively you keep an incremental backup on your server and give other computers limited privileges (they shouldn't have write access to snapshots).
- GnarfGnarf 12y ago
  Do your backups to DVD and you're guaranteed ransomeware can't touch them.
- bbcbasic 12y ago
  Good point. I would format any disk that has had ransomware on it before I did anything else (like plug in the usb drive with my backup). In the meantime use another PC to access the files. However yes it is probably worth having 2 backups for this reason, just incase you get caught short.