Check Your Hash at the Door

A friend recently asked if I would post about using md5deep; he was trying to figure out how to use it to compare against the NSRL hash library and was having some difficulties.  Well, maybe it's stretching to say he asked if I would.  He asked for some help in figuring it out, and at the end of it all, I offered to post some stuff; he said it might be useful.  So if I put a PR spin on it, I was specifically asked, because of my great and wondrous knowledge.  How's that?  :)

Oh, and if you're wondering at my use of the term "friend," you can always substitute "person who pretends not to hate me as much as others do" if that makes you feel better.  I know some of you don't think it's possible that I actually have friends, so I feel I have to give you a way out...

Anyhow, to be honest, I've not ever used md5deep for that specific purpose.  I've always used something like FTK or EnCase.  I know, I know, don't be hatin'.  I do a lot with command line tools, and prefer them in many - if not most - cases, but there are some instances where (completely dependent on the scenario), a GUI is just easier and/or the better option.  And for what I've done with the NSRL hash libraries, those tools were what was called for (there was more than just deNISTing at hand).  

That said, the way I've used md5deep should still accommodate comparing against the NSRL hashes, with just a little bit of tweaking.  I've always used it to compare and verify files being copied from various data sources (typically network shares), when using a copy application that couldn't do so.  So in that scenario, it works out something like this:

We want recursion, possibly a progress/status indicator, and an output file that can be used as the input file for hash comparison.

Hash the source like:

user> md5deep -re "g:\loose_PST_files" > f:\psthash.txt

Hash the destination (and compare to hash of source):

user> md5deep -renx f:\psthash.txt "f:\loose_PST_files" > f:\psterrorhash.txt

This breaks down as follows:
    -r = recursion
    -e = progress/status
    -n = displays names of files not matching the input file
    -x = negative hash matching; reports files not in the input file 

    g:  is the mapped or local source drive

    f:  is the destination drive
  
Order for source is:  > # the flags have to be combined together (ie, -re) or it errors.  It will automatically output to stdout, so we have to redirect to logfile; this gives filename and hash value only (other format cannot be read properly for use as input file).

Order for destination is:  >   # the error log immediately follows the flag as the first variable; this is read and compared against the hashes of the destination.  Any errors in the comparison (whether the file is there but shouldn't be, or isn't there but should be) will output to the error log.  The size of the log should be 0 KB when all is done, and (obviously) empty - thus showing there were no errors/mismatches. 

These were notes I made in the past, and I think were most recently updated with version 3.4.  The tool is now on 4.3, so I don't know if the following has changed, but ... as noted above, the md5deep comparison (input) file had to have hash value and filename only, or could not be properly read.  I couldn't find anything in the documentation to say one way or the other, but it's possible that the NSRL lists might be problematic, even though md5deep is only looking at the hash and not the filename/location.  I did have occasion recently to verify the integrity of some evidence migrated to new storage, and ran md5deep in the manner above; it worked great.  The only thing I'll note is that if you do want the progress indicator, it WILL slow down the process; use with discretion.  You have been warned.

There were a couple posts related to using NSRLSrvr and NSRLLookup that showed up on the radar.  The first I passed along, and the second my friend found on his own; apparently it was helpful.  I don't know the first author, but Patrick puts out some good stuff on Sysforensics.  If you don't keep tabs on his blog, you should.  So without further ado, here they are, and they should work just fine to use md5deep to compare against NSRL.

http://blog.jameswebb.me/2013/05/setting-up-forensic-hash-server-using.html

http://sysforensics.org/2013/12/build-your-own-nsrl-server.html

And this wouldn't be complete if I didn't mention the NSRLookup service from Kyrus Tech:

http://www.kyrus-tech.com/nsrlookup-service-beta/

Which I first saw mentioned last year on Jesse Kornblum's site:

http://jessekornblum.livejournal.com/278435.html?nojs=1

Have fun and happy hunting (or, uh, happy hashing)!

What's Hash Got To Do With It? (Part 2)

Just a quick follow-up to yesterday's post, as promised.  I decided to do it as a new post rather than an edit/update, figuring it would be easier to track this way.  Not much to it, just a little more info to round things out.

First, I got my hands on the infected PC today, pulled the hard drive, and extracted some files.  I wasn't able get RAM, but I do have hiberfil and pagefile to work with, along with the user profile and registry hives, but that's not the point here.  (I will note, however, that unless I can find evidence of the malware's activities in hiberfil or pagefile, I'm still - to an extent - surmising how it spawned msiexec.exe in the first place.)  I found three separate executables under the user profile, as created by msiexec.exe.  I copied them off into a separate directory and used md5deep to hash the files, so that I could look for them on VT or Malwr.com as well (there, now this is a post about md5deep too!).  Here's what I ended up with (my own formatting):

26e57bde90b43cf6dae6fd5731954c61 | msevaxlgn.exe  
26e57bde90b43cf6dae6fd5731954c61 | mssuhin.exe
26e57bde90b43cf6dae6fd5731954c61 | msyaam.exe

Did you notice that?  All hashed the same.  Okay, maybe that's expected, or not too unexpected at least.  But did anyone note the hash value from yesterday, for the initial executable (from inside the zip)?  Well, in case not, here it is again (in the same format):

26e57bde90b43cf6dae6fd5731954c61 | order_jd4320480293.exe

See that?  Yes, that's right - another md5 match, and I doubt it's due to collisions.  :-)  So basically, the original malware spawns msiexec.exe, creates a new executable(s) that is (or are) identical to the original (except for the name); the original is deleted, and the show goes on.  I don't know about you, but that's not what I commonly see from malware.

Now for a few more tidbits...

A little header info from a network capture:

POST /se/gate.php HTTP/1.1
Cache-Control: no-cache
Connection: close
Pragma: no-cache
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/4.0
Content-Length: 74
Host: finley.su

IP Addresses, as seen by the C2 blocking device:

Now, I mentioned before that there was a .ru TLD involved, and here that is:

Haven't looked at that traffic yet, and it never made it to the device that blocked the C2 traffic, as it had already been blocked for other reasons.  And of course, until I examine the pcaps, I won't know what that traffic was (still might not - since it was blocked, it will be a one-side conversation).

Last of all, a screenshot of the offending email (note some inconsistencies outlined in red):

SupportAmazonyu?  AmazonStoreIdecoa?  I could get it with "Amazon," but what's with the other stuff?  And the order numbers don't match up anywhere.  And finally, it says, "Well let ..." rather than "We'll let ..."

Well, I guess you can't patch users!  At least not without regression testing first.  ;-)

I think that's it for now; if I do come up with anything else that looks interesting or useful, I'll post another update.  Aside from that, I told a friend I'd post about some specific uses for md5deep; we'll see how that works out, but hopefully it will be coming soon.

Happy Hunting!

What's Hash Got To Do With It?

Well, because that's how we're going to kick off this little story.  Without further ado, here ya go:  26E57BDE90B43CF6DAE6FD5731954C61

Before we go too far into that, however, I need to take a step back.  It's been a long time since my last post.  Too long indeed (my job makes it difficult, to say the least), so let's not dwell on that, shall we?  With that out of the way, I'll give just a quick back story on the above-referenced md5 hash value.  Last week, on Wednesday and Thursday, I came across this malicious gem.  Well, I think it was the same both times.  From a network perspective, it was behaving the same - reaching out to the same C2 channels, attempting to post the same type of encrypted data (based on format, appearance of cipher-text, etc.).  However, as it turns out there wasn't an appropriate endpoint sensor on the first box, to be able to pull back more relevant info.

That fact is important as we go on - that unless you have evidence across different DFIR disciplines (host and network, with all their subsets), you really can't say for certain what is occurring.  You can postulate, and may very well be correct, but without RAM, RE, timeline and other host data, and various points of NSM (network security monitoring) such as FW logs, IDS/IPS, netflow, you're left at least somewhat in the dark.  Anyhow, from a network perspective, these two appeared to be the same, and fortunately there was an endpoint sensor on the second box; I got to have some fun, and thought I'd share.

As it turns out, the infections originated not from some stealthy drive-by or infected website, but via an executable inside a zip file sent along with an "Amazon" email to personal email accounts.  In the case of the second one, the user had received two previous ones that were ignored and deleted; the third was just too much and curiosity won out.  User opens zip file.  Oops #1.  User double-clicks executable.  Oops #2.  At that point it's all over but the tears, and the malware has its fun.  The positive side was that - finally - I got to have some fun too!

Now, I didn't know all that at first.  All I knew was that C2 traffic to finley.su had been blocked.  That was the same domain as the previous day, so my interest was piqued.  The system that blocked didn't have any info about the malware, just knew that the traffic was bad, so that was no help.  I went in to my sensor logs from that box, and found the application reaching out to finley.su was msiexec.exe, from the c:\windows\system32 directory.  Ooh, now that's not right.  The parent process for msiexec.exe was order_jd4320480293.exe.  Now that's not good either.  And it was running from inside a zip under the user's temp directory, with a parent of explorer.exe.  Alright, that's not unexpected, especially at this point.

I was able to pull a copy of the binary for order_jd4320480293.exe that the sensor had pushed to my analysis server, and saw that it had 9 hits by hash on Virus Total, so I went to check that out.  There were indeed 9 engines that detected it; one from the 11th, and eight from the 12th.  Most had generic names as yet; the most relevant one appeared to be from McAfee, which had it as a ZBot variant.  Searching on that lead me to Malwr.com, where the binary had apparently been uploaded and analyzed already.  As a side note, the next morning VT had 14 detections, and is now up to 23 (What's funny is that some of the vendors I submitted a sample to, now say they detected it back then.  Hmm, really?).  Since there's some RE type info on VT and Malwr, I won't try to go into that; I'll give you some reference links to go enjoy that.  I will, however, give a quick rundown of what I saw.  I will probably come back and add some IP addresses for the finley.su domain, as well as a .ru TLD I saw from the endpoint, so watch for an update.

So here's the quick high-level rundown:

*  User downloads zip from fake Amazon email, opens, and runs order_jd4320480293.exe

*  Malware executes, and order_jd4320480293.exe spawns (loads) msiexec.exe from c:\windows\system32 as a child process 

*  Child process msiexec.exe creates a new executable under the user profile, named (one example) msyaam.exe or msevaxlgn.exe (another example)

*  Child process msiexec.exe adds a runkey for the new executable, in the user hive, under Software\Microsoft\WindowsNT\Current Version\Load

*  Child process msiexec.exe deletes original executable, order_jd4320480293.exe

Along in there somewhere, msiexec.exe packages up some data (probably credentials), encrypts, and tries to ship it out to remote servers.  Unsuccessfully.  Defense in depth... ;-)

Well, that's it for now.  Given the info available elsewhere about this malware, I probably won't post anything about its actions on the system, unless I see a very different  approach take place.  But I will look to post some IPs and perhaps some other tidbits that might be helpful from an IOC perspective.  Other than that, here are some links:

Virus Total:  https://www.virustotal.com/en/file/00fb48cae855a1321e9edcd2b0d9a4935dc7954f0221030a3b01dbdfe0332a44/analysis/ 

Malwr:  https://malwr.com/analysis/MDU2ODNhYzA1MmIzNGZiYTkxNmQ5OWJmNGM0OWFiNGU/#static

Sophos:  http://www.sophos.com/en-us/threat-center/threat-analyses/viruses-and-spyware/Troj~PWSZbot-X/detailed-analysis.aspx

Happy Hunting!

Getting Your Feet Wet / Joining the Conversation

Well, I've been "working" on this post for quite some time now, and just haven't ever wrapped it up.  Bah.  To show how long I've been "working" on it, I came up with the idea before Richard Bejtlich posted on the Mandiant blog about InfoSec career building and before Chris Pogue posted about his job change (and where he hinted at the possibility of a "Sniper Forensics" book - bring it, Chris!), or about careers (his 2nd post on this topic).

Part of this comes from a comment that Hal Pomeranz made a while back.  He said (general paraphrase) that there's no better use for social media than to help others.  In context, he was talking about InfoSec jobs.  Hal's a guy that I highly respect, and since I've witnessed - first hand - his willingness to put his money where his mouth is (so to speak) in this area, I take it to heart.  By the way, he has an excellent series on working for yourself over on his blog (keyword: consulting).

A number of great folks have posted career-focused info, including those above, and it's more recently entered my radar as I'm in more of a position to help others.  I don't have the "street creds" they do, but I wanted to offer up a few things I've put together.  As I moved late last year into managing our InfoSec group, as well as heading up the IR team, I've had the opportunity to mentor a couple of newcomers to our field, and I put this together in part for them, to give them some additional resources.  I highly agree with what others have said, that putting yourself out there is important - blogging, tweeting, mailing lists - just talking and sharing with others.  I won't go into that in any depth, as I think it's been very well-covered elsewhere; I'll just re-emphasize that it's important.  I've seen it myself, where potential employers check out blogs, activity on email lists, and so on; it definitely makes a difference, because hiring someone in this field revolves around having confidence that they KNOW what they're doing, and can DO the work.

So with that said, if you're new to InfoSec (security, forensics, incident response, auditing, etc) here are some resources that can help you start to get more comfortable and plugged in to the community.  And it IS a community, more so than many other fields I've seen. 

Mailing lists:
Dragon News Bytes
PaulDotCom
Win4n6

Websites:
DFIR Online - this is an excellent resource, and also hosts the monthly "DFIR Online"
PaulDotCom - yes, it's showing up again  :-)
SecurityFocus
Darknet
CommandLineKungFu – this is just awesome and hilarious too
HolisticInfoSec - Russ has some great tool writeups
KrebsOnSecurity - Great resource on cybercrime
Team Cymru
US Cert
SANS Reading Room
Internet Storm Center
Jesse Kornblum
Lenny Zeltser
SANS Computer Forensics
ForensicArtifacts
A Fistful of Dongles
Hacking Exposed

Books:
The Basics of Information Security
Hackers Beware – older, but very good info
Network Security Bible – another one by Dr. Eric Cole
DFWOST
Hacking Exposed - any of the "Hacking Exposed" series
WFAT - any of Harlan Carvey's books
Practical Packet Analysis
Violent Python
I’ve found great deals on books at Half-Price Books, which can make a big difference.  Some of the older ones, you might be able to find at the library as well.

Twitter:
I really recommend you get on twitter if you’re not.  Have a profile that’s focused on what you’re interested in, and follow people in that field.  It can be a great source of information, as well as connections when you need to know something.  Here are just a few folks that may be good to start with:
Johannes Ullrich
Josh Wright
Lance Spitzner
Russ McRee
Wesley McGrew
Doug Burks
Christiaan Beek
Eric Cole
Brian Krebs
Mike Cloppert
Richard Bejtlich
David Cowen
Didier Stevens
Lenny Zeltser
Hal Pomeranz
Chad Tilbury
SANS Forensics
Rob Lee
Andrew Case
See who they're talking to, and start branching out with who you follow.  Don't be afraid to join a conversation, ask questions, and share your experiences.  There are also quite a few active DFIR types on Google+, and there have been some good conversations happen there (at more than 140 characters a pop), as well as some hangouts.

Hope you find it helpful.

PS:  I have been advised by Counsel to at least mention that this list of resources is by no means exhaustive, nor intended to be.  In addition, they are in no particular order, nor intended to be any sort of status qualifier, and I'm not getting paid in any way for these references (aka, name dropping).  They are just some of the resources I find helpful, and wanted to share.  If you , your site, your book, or your list are not mentioned, that doesn't mean I don't follow, read, etc (see the whole "not exhaustive list" piece).  There are several hundred folks I follow on twitter, over a hundred blogs, dozens of books, and websites galore where I gather info while on this journey.  Quite simply, too many to mention.  Thanks to you all for being available and sharing with the community!