Monday, May 31, 2010

Carders.cc - General Observations and Updates - Part 3

Digging into this data is like watching an episode of Lost. Whenever it seems like one question gets answered, about ten other questions pop up.

Before I get into details, I want to start with a comment Per Thorsheim sent me as to what other password cracking programs support salted sha1 hashes:

The sha1(lowercase_username.password_guess) is at least supported by these:

Extreme GPU Bruteforcer (www.insidepro.com) hashcat and oclhashcat (cpu/gpu respectively) www.hashcat.net

I'm kicking myself for not thinking about hashcat, since it's a extremely powerful password cracker; plus it's free. Unfortunately the GPU version doesn't support the salted sha1 hash type, but even the non-gpu version is quite nice.

As for InsidePro, it also is very good, though it does cost some money. I've had a license-free version of questionable origin offered to me before, but I turned that down. Legality aside, installing pirated software given to you by shady people at a hacker conference would just be stupid...

Also, I've been talking to Ron Bowes over at the excellent skullsecurity blog, and he and some other people are hard at work cracking the passwords. It sounds like they have some serious hardware behind the effort, so expect to see something posted on his site about that in the near future.

OK, now onto the analysis:

First of all, I'm downgrading my opinion of the skill showed by the hackers in their password cracking attack. What I didn't realize before was the extent that the users of carders.cc had been compromised previously. Just about all of the non-trivial passwords that were cracked appear in publicly available input dictionaries which are based on passwords cracked from user submitted hashes - aka hashkiller, insidepro, etc. Please note, I'm not saying they were script kiddies. The attackers were able to target the salted sha1 hash, and they knew where to get some good input dictionaries. It's just that they are not some uber-l33t password crackers, and anyone else using those input dictionaries could crack the same number of passwords in a couple of hours.

What this also means is we might be able to figure out which input dictionaries the attackers were using by looking at the hashes they cracked, vs. what the input dictionary would crack. To demonstrate this, below is a Venn diagram of what an input dictionary the attackers used would look like:


For example, there is a good chance the attackers used the InsidePro Big dictionary, since it cracks the same 598 passwords from the carders.cc list that the attackers cracked. Add in a couple of the other publicly available input dictionaries, and you get real close to the 920 total passwords they managed to crack. To put this in perspective, I've so far managed to crack 62%, (compared to the 53% that the hackers cracked), of the salted Sha1 passwords on my laptop using basic dictionaries with almost no mangling rules. I fully expect other people to blow past that mark.


Next up, initial thoughts about the carders.cc database:

What I really need to do is load all of the tables into my own database so I can do quick SQL queries, vs. manually going through the data by hand. That being said there are a few things that stick out:
  1. There's a lot of userids/password hashes in the carders_smf_members table that did not appear in the write-up.
  2. The MD5 hash is salted, but at least the salt is also available in the carders_smf_members table. The hash itself is a vBulletin3 hash type, MD5(MD5(Password).Salt). Both John the Ripper and Hashcat support this hash type.
  3. I'm not sure if the IP addresses stored in the table are accurate or not, since it looks like the site admins tried to obscure it in the webserver logs, but if they are, the database stores the last two ip addresses used.
  4. Other interesting fields include date joined, number of posts, karma level, last login date, etc.
  5. The above doesn't even begin to get into all of the data contained in the actual posts themselves...
That about it for this update. Let me leave you with one last fact that Ron found out:

Another interesting factoid:

Last MD5 password: 2010-01-10 21:54:01

First SHA1 password: 2010-01-10 22:40:16

So it was on January 10, 2010, later in the evening (in CDT) that they upgraded from vBulletin 3 to SMF.

*shrug* the more you know!

Wednesday, May 26, 2010

Carders.cc - Analysis of Password Cracking Techniques - Part 2

So I figure I probably should get around to looking at the passwords in this list, since password cracking techniques are the focus of this blog...

First though, a real quick definition. I needed to decide what to call the various parties involved in this whole shenanigans. For example, when I'm talking about the 'hackers', am I referring to the people collecting stolen credit card data who belonged to the board, or the people who hacked carders.cc? Likewise, if I use the term criminals, that could refer to both groups as well. Therefore, in my blog posts I'm going to use the following terms to refer to the two groups:
  • Carders/Users: The people who belonged to the board. Normally I would also use the term 'victims', but I don't want to honor them with that title.
  • Hackers/Attackers: The people who broke into the forum and posted the data online.
Ok, now that we have that out of the way, the rest of this post is going to be broken up into four parts:
  1. Executive Summary
  2. Brief Description of the Password List
  3. General Observations
  4. Setting Up a Password Cracker to Target Salted Sha1 Hashes
More in-depth analysis will have to wait till later since I need more time to go through the data. Also, I'm moving up to the D.C. area in a week to look for a job/start interviewing, so large scale password cracking sessions are not really feasible for me to perform right now.

-BTW, if you have a job opening please feel free to contact me.

Finally, I apologize but this post is going to be a bit more haphazard then the above outline implies, simply because it's hard to talk about one aspect of this dataset without discussing other aspects as well.

Executive Summary:

Carders.cc, on online forum for the buying and selling of stolen bank and credit card data, was broken into sometime before May 5th by vigilante hackers. On May 18th, the hackers then posted data about the users to various file sharing sites, (pastebin, rapidshare), which included IP addresses, usernames, e-mail addresses, and all of the saved forum posts. More significant to this report, the attackers also posted the users' password hashes along with the plaintext passwords that the attackers had managed to crack. These passwords and password hashes provide significant data for researchers. From this data, we now know that cyber-criminals often select weak passwords. Furthermore, by analyzing these passwords we can develop better password cracking techniques that target the specific type of users, (criminals), whom law enforcement is the most interested in. This is an improvement from some of the other disclosed password datasets which were gathered from the general public. In addition, by looking at the passwords the attackers managed to crack, along with the passwords they failed to crack, we can gain a better understanding of the capabilities and techniques employed by hacker groups in real life attacks. This hacker group in particular appears to be quite proficient in password cracking techniques, possessing both the tools to attack salted SHA1 password hashes, and the ability to crack close to 53% of the passwords in the dataset.


Brief Description of the Password List(s):

The first thing that stands out is there are actually two lists of passwords present in the attacker's write-up, though all of the password hashes are mixed together.

List 1)
Contains 1737 salted Sha1 password hashes using the following format:

Sha1(username.password)

This is the list that the attackers talked about and the list they attempted to crack passwords from. Of all the salted Sha1 password hashes, the attackers cracked 920 of them, (around 53%), during the course of an approximately two week period.

List 2)
Contains 2036 "one hundred and twenty eight bit" password hashes of unknown origin. Due to their length, the base password hash is most likely MD4 or MD5. It is unknown if the attackers knew of the existence of these separate hashes since they did not mention the second hashing function in their writeup or crack any of the passwords from this list. I've run some quick tests and these hashes do not appear to be a single round of MD4 or MD5, but probably instead are salted in some manner, and/or use multiple rounds of MD4/5. If a salt that was not the username was used, then it probably will be infeasible to crack very many of the passwords due to the salt not being included in the writeup. A few of the passwords might still be vulnerable though since the salt may be short enough to be brute-forced along with the guesses.
So the next question is, why were there two separate types of password hashes? The most likely explanation is that at some point in the past, the site administrators switched over to a new forum software, or upgraded their security settings. The old users were left with the original password hash, and users who joined up afterwards were assigned the newer password hash. The exact same thing happened when phpbb.com was hacked, leaving users who hadn't logged into the site recently, exposed with only a simple MD5 hash protecting their password vs. the tougher phpbb3 hash.

The interesting thing is that in this case, a user's hash probably was not changed to the new format when they logged into the site. This can be seen by comparing the user's hash type to the IP addresses I talked about earlier. Of the 960 username/IP address combinations, 47 of the users had their password stored as the unknown hash, and 726 had their passwords stored as a salted Sha1 hash. You might notice that these two numbers did not add up to 960. There were 187 usernames that appeared in the IP logs but did not appear in either list of password hashes. I need to look into this more, but many of them might represent incorrect login attempts. A second option is the attackers may not have released all of the user password hashes, instead choosing to keep several for themselves to aid in future hacking attacks. I should probably analyze the forum posts to confirm if the hash type correlates to when the users became active, and if any of the users with missing password hashes actually posted previously on the forum.

Why yes, this is my "brief" description...


General Observations:

Observation 1) The attackers are very proficient in password cracking techniques
Level of Confidence: High
Discussion: The fact that the attacker could even target the salted Sha1 password hashes speaks to their competence. Most major password crackers, (Cain&Able, John the Ripper, L0phtcrack, etc), do not natively support that salt/hash combination. While John the Ripper has extensive support for a generic MD5 hashing function, where it is very easy to modify it to support all sorts of weird hash/salt combinations, that functionality has not yet been ported over to support Sha1 as well. So either they developed their own password cracker/workaround, (which isn't as hard as you might think, as I'll discuss later), or they had access to a less well known password cracker that supported that hash.

Question: Does anyone know of any password cracking program that does support Sha(username.password)?

In addition, since the passwords were salted with a unique salt per hash, this negates many common attacks like rainbow tables. Also, I don't know of any online password cracking site that supports this hash format, since they can't use hash lookup tables either. This means the attackers had to crack all of the password hashes themselves instead of relying on community resources.

Next, the fact they cracked 53% of the password hashes in a two week period speaks highly of the attacker's skills. To put this in perspective, in the phpbb.com attack, the attacker had submitted unsalted MD5 password hashes to an online cracker and only managed to crack 24% of the passwords. In that case, while the hacker might have been very skilled in webpage attacks, they were pretty much at the script kiddie level when it came to cracking the passwords. While 53% might not sound that much more impressive, there is the fact that in the carders.cc case, the hashes were salted with a unique salt. The 'unique' part is important since it means an attacker has to hash each guess independently against each target hash they are trying to crack.

For example, imagine a typical cracking session taking one hour to complete. If an attacker was attempting to crack three thousand unsalted password hashes, then it would take them one hour to run all of their guesses against the entire list. On the other hand, if those password hashes used a unique salt, the same attack would then take three thousand hours, or roughly four months. That's a big difference. Assuming the attackers spent two weeks attempting to crack all 1737 salted Sha1 password hashes, that would mean the guesses they could make in their attack would be equivalent to a 11 minute cracking session against unsalted Sha1 passwords. Even assuming they cracked 50% of the password almost immediately, their cracking session would still be only equivalent to around 20 minutes of attacking unsalted hashes. In conclusion: cracking 53% of close to two thousand salted password hashes in a two week period is fairly impressive.

Observation 2) The Attackers did not user John the Ripper's Incremental mode to brute force guesses.
Level of Confidence: High
Discussion: When I ran JtR's incremental mode, using the default charset 'All', against the list, I almost immediately cracked a new password. Over a longer running session, I managed to crack even more.
Observation 3) The Attackers brute forced digits
Level of Confidence: Low/Medium Very Low
Edit March 28th 2001: I've since managed to crack the password '37721010'. It appears that most of the longer digit based passwords that the attackers had cracked were publicly available in lists of previously cracked password. I'm leaving my original discussion post up for posterity.
Discussion: I have not yet been able to crack any all-digit passwords that the attackers did not crack. Likewise, the attackers cracked several passwords such as '19930720', where unless the attacker has outside information, or had run across that password earlier, it is unlikely to be cracked by any form of attack besides brute force.
Observation 4) The Attackers did not brute force alpha passwords longer than five characters long
Level of Confidence: High
Discussion: I have since managed to crack several passwords that were four lowercase characters long followed by two digits. Likewise I managed to crack several passwords that were six characters long all lowercase.
Observation 5) The attackers may have used knowledge from previous attacks to aid their password cracking sessions
Level of Confidence: Medium
Discussion: Let's be honest, this isn't their first time at the rodeo. It's doubtful that carders.cc is the first blackhat site these attackers have compromised. As we've seen from the ZF0 attacks, just because a website supports a tech-savy audience, doesn't mean it stores their passwords securely. And as we all know, people re-use passwords ... a lot. It's quite possible that the attackers used passwords cracked from previous sites to in turn crack some of the passwords in the carders.cc set. For example, one of the cracked passwords was 'Nadia2312'. An unsalted MD5 hash of that same password was cracked via the Hashkiller site's project Opencrack, on February 1st, 2010. While it could be a coincidence, I'd also like to point out that Hashkiller is a German based website. Other plaintext passwords in the list such as '123456r12', and '01724776692' also show up as being cracked by HashKiller and InsidePro in 2009. Note, this may just imply that the attackers used custom input dictionaries from these sites, and did not actually submit the original password hashes to them.

Setting Up a Password Cracker to Target Salted Sha1 Hashes

As I mentioned previously: I'm sure there's already a password cracking program out there that can target salted Sha1 hashes, but I don't know of it. Not to be deterred, I quickly modified an old password cracking program I had written a while ago to support the hash, (note I could have modified John the Ripper instead, but I'll get to that in a bit). The hardest part was I didn't realize that when you added the username as the salt, you had to lowercase the entire thing. That's a couple of hours of my life I'd like back...

So testing this on my Mac laptop I expected to be able to make around 1000 guesses a second against the entire set of 1737 password hashes. I based this guess on benchmarking unsalted Sha1 hashes using John the Ripper, which gave me around 7,000,000 guesses a second. This would give me a maximum of 4029 guesses a second against the salted hashes. Throw in the overhead required to apply the salt plus my general programing sloppiness, and 1000 guesses a second sounded like a good number. So you can imagine my surprise when i was only ended up making around 80 guesses a second. Something's not right here...

Well it turned out, the problem was I had used the OpenSSL implementation of the Sha1 hashing algorithm which is really slow compared to the version in John the Ripper. Rather than trying to jury rig it into my old password cracker, I then decided to work with John the Ripper instead, which is what I should have done in the first place.

Since I'm a bit lazy goal oriented, I didn't bother to modify John the Ripper's source code though. I was able to get away with this since the hashing algorithm only uses one round of Sha1. Let's look at the hashing algorithm again:
Sha1(lowercase_username.password_guess)
The simplest way to do this would be to create a rule in JtR that would insert the username first. Such a rule would look like:
A0"alice"
Which would insert Alice in front of all of your password guesses. Since we have close to two thousand usernames we are talking about though, that could get annoying having to create a rule for each one. This calls for the use of one of my favorite programs, Awk.

Awk, (and its sister Sed), is one of the best programs out there for quickly parsing and modifying files. It's also very useful for creating word mangling rules on the fly for use in a password cracking session in conjunction with JtR's stdin option. In that way, I sometimes use it much like MiddleChild, and in retrospect, I could easily have written MiddleChild in awk instead. For example I can create guesses using John the Ripper, pipe them into an awk script, and then pipe them back into John the Ripper where the guess will actually be hashed and compared against the target hashes. The above JtR rule could then be replaced with:
./john -wordlist=passwords.lst -session=cracking1 -rules -stdout | awk '{print "alice" $0}' | ./john -stdin -format=raw-sha1
The advantage of this approach is that 'alice' will be automatically inserted in front of all the guesses/rules that the first instance of John the Ripper is generating. But wait, don't we still have close to two thousand usernames we have to do this for? That would be one nasty command line. Luckily an Awk script can be run from a file with the -f option. And how do we create that file with all 1737 usernames? Well with Awk of course! The original format that the hashes were saved to in the carders.cc writeup was:
username:hash:plaintext:e-mail
Simply cat that file into Awk using the following command will create your Awk script for you.
cat carders_hashes.txt | awk -F : '{print"{print \"" tolower($1) "\"$0}"}' > awk_add_usernames.txt
The -F tells it to use the ':' as a seperator and the tolower() option lowercases the usernames. To run this whole thing just type:
./john -wordlist=passwords.lst -session=cracking1 -rules -stdout | awk -f awk_add_usernames.txt | ./john -stdin -format=raw-sha1
Using this setup, now I'm getting around 2,300 guesses a second which is much more respectable. There certainly is room for improvement though. First of all, John compares each hashed guess against all of the target hashes, instead of only the hash which the salt belongs too. Also, you have to clean up the cracked hashes file afterwards to remove the username from the plaintext password. But did I mention it works? As Miles said in the Lost finale, "I don't believe in a lot of things, but I do believe in duct tape!"

Well, that about does it for now. Next up, analysis of the cracked passwords.


Tuesday, May 25, 2010

Carders.cc - Analysis of E-mail Addresses

I just wanted to point everyone over to Cedric Pernet's bog where he did an amazing job analyzing the e-mail addresses that the carders had used. You can view his work at the following link:


It shouldn't come as a surprise, but just because someone is a cybercriminal doesn't mean they are smart.

Also, if you or anyone you know is doing research into this, feel free to forward me the links. I only found Cedric's blog on a reference in another post on page 8 of a Google search I did, (aka I stumbled on it by pure luck). Thanks!

Sunday, May 23, 2010

Carders.cc Hacked - Initial Analysis of IP addresses

As the title says, Carders.cc, a German forum for the buying and selling of stolen credit cards was hacked and a ton of information was posted publicly online. For a more detailed description, I highly recommend reading the always excellent Brian Krebs writeup on the incident.

I'm going to skip right past my feelings on the subject. The short version is, while part of me is laughing inside, I tend to think such vigilante justice is often counter-productive. I just wish people like that could work with the system because by doing so you can sometimes achieve spectacular results.

Instead I'm going to focus on the data itself and what it can tell us from a research perspective. So far I've managed to download the writeup of the attack, which also includes IP addresses, usernames, e-mail addresses, and password hashes. I'm also currently in the process of downloading what I think is the listing of all the private messages, though it may just turn out to be viruses and fail. BTW, that's why I love VMWare. Edit: It's legit, and wow. It's going to take me a while to sort through/make sense of that data. Expect a post on that later. Google translate, don't fail me now!

As a word of warning, just about everything in this post falls into the category of WAG. While I try to create these guesses with the data I have available, please take everything I say here with a grain of salt. The uncertainty level is HIGH.

First of all, here is a picture of the writeup so you can all enjoy the ASCII art:



So what do we know? From the file timestamps in the writeup, the site was probably compromised sometime around May 5th, (though of course the initial attack could have occurred earlier.) The pastebin copy I downloaded was uploaded on May 18th, so this gives us a general timeframe which will be useful when we start talking about the password cracking that went on.

Question: Does anyone know where/how the attack was initially publicized? Was it a site defacement, posting in a rival forum, etc?

Before I get sidetracked talking about password cracking the hackers did, let's look at those IP addresses collected from the various users of the forum. These IP addresses were only collected for the users who logged on to carders.cc between May 11th and 12th. Starting out, the simplest thing to do was to run a basic GOIP lookup on the countries associated with them. The results can be viewed in the following graph:


As you can see, it really was a mostly German based forum. Not a big surprise I know, but it's nice to see where everyone is coming from. The next thing I wanted to look into was how many duplicate IP addresses there were. This would imply a forum goer was using multiple usernames, or a common proxy that several of the carders were connecting through.

Of the 960 published IP addresses:
  • 819 of them were unique
  • 25 of them were associated with two user accounts
  • 10 of them were associated with three user accounts
  • 3 of them were associated with four user accounts
  • 2 of them were associated with five user accounts
  • 1 of them was associated with seven user accounts
  • 1 was associated with eight user accounts
  • 1 was associated with eleven user accounts
  • 1 was associated with thirteen user accounts
Thirteen user accounts to one IP address? As the Germans would say: "That's a Bingo". The IP address in question, 92.241.164.47, has been previously detected by Project Honeypot as a prolific Russian based Mail, and Blog spam sever. It's on most IP blacklists by now, so I guess they also use it as an anonymous proxy sever to keep their revenue stream up. The other heavily used IP addresses showed similar characteristics. What I found particularly interesting was the following pastebin link I stumbled across when Google searching those IP addresses. It was posted on February 28th, and contained three of the proxy servers that the carders used.

The IP address I have the most questions about though was 193.105.134.54, which is a Swedish IP where eight of the users connected from. I couldn't find any past abuse originating from that site. When looking at the user-accounts/e-mail addresses associated with those IP addresses, another interesting thing popped up. The user "Risking", didn't have an associated password hash/user account listed in the writeup. My guess is that the hackers dumped the hashes fairly early on, (probably around May 5th), but didn't figure out how to grab the IP logs until May 11th. In that time the user Risking probably created a new account.

So we know some of the users were smart enough to use proxy servers. How about Tor? Downloading a list of all of the known Tor routers was fairly easy, so all that remained was to compare them to the IP addresses in the writeup. All in all, there were 20 unique IP addresses that matched known Tor IP addresses. That's actually a lot lower than I expected. Of course the question then is, how were a majority of users connecting to the site? Smaller proxy servers? Public cyber-cafes? Starbucks? Their neighbors wireless? Were they really dumb enough to connect from their home accounts? I don't know the answer to that, but hopefully someone with more experience investigating blackhat forums will post their analysis/experiences on the subject.

So that about does it for IP addresses today. The database containing all of the downloaded messages looks like it also contains IP addresses too so I might revisit this subject soon. The next topic: An analysis of the hacker's password cracking attacks against carders.cc.

Wednesday, May 12, 2010

They'll Let Anyone Graduate: My Password Cracking Dissertation

You've all heard me complain/stress out about writing my dissertation, so now that it's done of course I'm going to post it online. My PhD. dissertation, "Using Probabilistic Techniques to Aid in Password Cracking Attacks" is available for download from my tools page here.

A lot of it is going to look fairly familiar if you've seen my talks or been reading this blog, which makes sense since my dissertation is a summary of what I've been up to for the last three years. Here's a quick breakdown of what's in it:

Chapter 1:
  • Overview + background info
  • The need for password cracking
  • General terms and techniques
  • Obtaining the datasets, and basic statistics about the datasets
  • A quick survey of common password hashes and popular password cracking tools
Chapter 2:
  • Brute Force Attacks
  • 95% of it I've talked about on this blog before
  • The remaining 5%, which I really should post an entry on, is a comparison of a targeted brute force attack against a pure Markov attack. The targeted attack uses the tool I previously released, MiddleChild.
Chapter 3:
  • Dictionary Based Attacks
  • Summary of some of the custom dictionaries I've created plus tools. Most of the tools are available in various places on my tools webpage.
  • Mostly this chapter focuses on the use of a customized edit distance metric for evaluating the effectiveness of input dictionaries, which is something that I've found incredibly useful.
  • Being a total of nine pages long, this is the chapter I feel is the most incomplete. It's also why I'm glad I have a blog so I can rectify that shortcoming over the next couple of months with additional posts ;)
Chapter 4:
  • Dictionary based Rainbow Tables
  • For the complete AV experience, a video of me talking about this at Shmoocon is available here.
  • Quick note: I've since figured out that the higher number of collisions caused by the dictionary tables was due to the fact that I was comparing them to "perfect tables", aka ones where all of the merging chains had been removed. If I remove merging chains from the dictionary tables, they perform just as well, collision wise. The fact that I didn't realize this when I was running the tests is a bit embarrassing. #facepalm
  • I have a bunch of ideas on how to further improve my tables, such as adding targeted brute force support, (with Markov Models!!), and enhancing the basic dictionary attacks with more advanced word mangling rules and multiple dictionaries. Implementing those is very high on my todo list.
Chapter 5:
  • Using probabilistic context free grammars for password cracking
  • Instead of focusing on the word mangling rules, focus on the probabilities instead
  • The result is a password cracker that can be trained on previously disclosed passwords and generates highly targeted guesses
  • This is the heart and soul of my dissertation and the reason why I graduated. If you only read one chapter this should be it.
  • Why should you care: It cracks more passwords with fewer guesses. What's not to like?
Chapter 6:
  • A critique of NIST's use of entropy as a password strength measurement
  • Essentially a very rough draft of the paper I submitted to the ACM CCS conference on the effectiveness of different password creation policies. I started running the tests/writing this section about two weeks before I defended, so I've collected a lot of data since this chapter was finished.
Sot that's about it for three years worth of work. It's a bit humbling I have to admit, since there's still a ton of stuff I still want to look into/implement. Luckily, just because I graduated doesn't mean I have to stop my research. Here's looking forward to the future.

E-mail Address Change

Since I'm graduating, I was informed that I might not be able to keep my weir@cs.fsu.edu e-mail address. I'm trying to see what I can do to hold onto it, but for the time being I'd recommend e-mailing me at reusablesec@gmail.com.