Posts

Brush up on Dropbox DBX decryption

Few weeks ago I was contacted about how to decrypt Windows Dropbox DBX files and the same topic appeared on SANS DFIR mailing list too. So I decided to create an Open Source toolkit and this post to brush up on the DBX files create by the Dropbox client on a Windows machine.



The Windows Dropbox client keeps its own files - user info, configuration, 'my dropbox' files sync status and even more - inside the user profile: on the Windows 7 and Windows 10 machines I used for test they reside in '\Users\%USERNAME%\AppData\Local\Dropbox\' and sub folders. Among them there are files with .DBXextension, which are the target of this post. When you take a raw look at them, you see garbage, noise... encryption is in place.

Without too much suspence, this is well-known. Nicolas Ruff and Florian Ledoux had a talk at hack.lu2012 on the topic, “A critical analysis of Dropbox software security” (here). They discovered that the encryption key used for DBX files is kept in the registry

Analysis of a Dridex maldoc pre-Locky

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The latest trends on the security threat landscape have mainly been Ransomware distributed via infected websites, and Banking Trojans distributed via malicious documents attached to phishing emails. In particular, Dridex banking trojan has been one of the most active threats. Last week the two threats merged and Dridex began distributing Locky ransomware as well.
In this post we will go through the analysis of a malicious office document delivering Dridex banking Trojan, spreading just the day before it switched to Locky and we will the similarities between the two actors that make us believe the same is behind the two.

Introduction On Friday February 12th, we observed a big wave of phishing attempts, over 700, which looked like the following:
Sender: fpo.cc.XX@vosa.gsi.gov.uk
Subject: DVSA RECEIPT
Attachment: Fixed Penalty Receipt.docm
MD5 Checksum: 50e1c94e43f05f593babddb488f1a2f9

Where XX are two random digits. Few days later, on Monday February 15th, we observed a second bigger wave, …

Windows ReVaulting

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Windows Vaults and Credentials allow the user to store sensitive information such as user names and passwords , that can be later used to log on web site, services and computers. In this post it will be shown how such data is protected and how you can decrypt it offline.

This post is a very late debriefing of the talk I had at SANS DFIR Summit Prague 2015 and it's the first of two posts. You can download the slides from SANS Summit Archives or from SlideShare.


introduction
I've never used Vault/Credential facility on purpose, even if the system used it without my knowledge : it's worthwhile to know that Windows autonomously uses it almost every day. In any case, we can find sensitive information there, and this is the reason I started this research, as to have a little more strings to my ODI (Offensive Digital Investigations) bow.

Windows provides two utilities to manage such credentials, the graphical Credential Manager and the command line vaultcmd: you can see them in the n…

Rekalling Mimikatz

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I'm not really sure that everybody knows that Rekallmemory forensics framework contains a Mimikatzplugin: with this post I want to address this shortcoming, since the plugin has many good features and it can be easily extended.

behind the scenes
The act of rekall-ingMimikatz started when I met Michael Cohen in Prague (SANS DFIR 2014) and a few months later in Dublin (DFRWS 2015). Despite the fact that I learnt so much by speaking with Michael, he deserves the credits to have pushed this plugin development: he released a first version on April 2015, based on what I did with Volatility (see et voilĂ  le mimikatz offline). So by hangout-ing during the night, we co-authored the actual Rekall mimikatz plugin: it was an awesome dive in Windows memory and Rekall internals, guided by Michael who truly has a talent for explaining complicated things in a simple way.

Before going further credits and thanks must go to the awesome reverse engineering research made by Benjamin Delpy: the plugin …

Windows Phone PIN cracking

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Windows Phone 8 and greater allows the user to lock/unlock the phone by using a numeric PIN code: it's even possible to use a complex alphanumeric password. This post addresses how to obtain the simple numeric PIN code by cracking the authenticator kept in the SOFTWARE hive.
an useless quest?
Actually if you have a physical access to a Windows Phone you don't need the user pincode to examine the user data: with the proper hardware you can usually get a whole dump of the un-encrypted device memory. To my current knowledge the pincode is not used anywhere if not for device locking, so it's almost useless to know it. If the device is under a properly configured MDM, you could face a fully encrypted phone with TPM: in this case you'll have no chance to crack the pincode, even if more testing should be done.

This is exactly what I thought when my colleague Mattia Epifanitried to lure me with the Windows Phone PIN issue: he knows the curious monkey inside me... but I was a re…

A first look at Windows 10 prefetch files

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Windows 10 prefetch files (*.pf) show a different file format compared to previous ones.  At first glance you'll spot notextualstrings inside, and this was the initial reason that make me try to understand how they changed.

quick&dirty journey

I guess that neither you nor I will run into Windows 10 DFIR cases for a while. That's what I thought when Claudia Meda(@KlodiaMaida) contacted me, showing me a couple of Windows 10 prefetch files. She then provided me some interesting clues that tickled the curious george monkey in me. Officially I do not have spare time, since it's already allocated, so I illegally used the non-existent spare time of spare time: please don't betray me... so I hope you'll tolerate any shortcuts in my quick&dirty journey into the entrails of windows (disgusting, isn't it?).

first lead
First, what a nude prefetch file has to say? Check the first bytes in the next figure, which shows a prefetch file for calc... sorry, now it's calc…

iOS 8.3: the end of iOS Forensics?

The latest iOS update (iOS 8.3) is a real nightmare for digital forensics specialists. This article will try to clarify what can you really obtain from an iOS device with iOS 8.3.
As we already know from Jonathan Zdziarski blog, with the introduction of iOS 8 is no longer possible to obtain a so called "Advanced Logical" acquisition based on lockdown service.

However, when we find a device without passocode it is still possible to obtain a backup, although it may be password protected if the user has previously set a password for the local backup.

In the same way we can perform a backup if we find a turned on and locked device, but only if we are able to find a pairing lockdown certificate and the device has been unlocked at least once by the user before the seizure. The same problem about an eventual backup password previously set by the device owner applies to this case too.

The real nightmare is when, and this is the most common case, we have to acquire a device that was turn…