Investigating Windows systems with Linux

Revealing Mozilla

Firefox stores its data in history.dat. The first column contains the date and time information in Unix timestamp format. The third command in Listing 6 converts this to a human-compatible format. Dumphive [12] provides an approach to making the registry on a Windows system more easily readable (Figure 4). The dumphive /mnt/WINNT/system32/config/system system.txt command stores the register in a separate text file, which the investigator can probe using Unix text tools.

Windows Passwords

Access to the system is interesting in its own right, but discovering the user's passwords often opens up other vectors to the investigators, as most users don't bother changing their passwords when they log in to various websites and services. On top of this, passwords give the forensics investigator the ability to log in to a virtualized image system on VMware and to investigate various system logs and files.

In addition to employing brute force attacks and tools like John the Ripper, which use dictionaries or rainbow tables, the Linux admin can turn to other tools such as Bkhive, Samdump2, and Ophcrack [13].

Extracting local passwords from a SAM file is not hard, as used by Windows NT-based operating systems, especially if you combine various tools. For example, John the Ripper automatically detects a Windows SAM file if you feed it to the tool. The Microsoft-specific password genus is useful here: Although Windows credentials can be up to 14 characters, the system splits them into two strings of seven characters each. This is a useful contribution by the manufacturer that makes it easier for investigators to break passwords without extreme number crunching.

As of Windows Vista, Microsoft closed this gap and replaced the Lanmanager hashes with NT hashes. XP admins can set this up manually; investigators on Linux have to run dumphive to check whether the Registry contains an entry that sets HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/Lsa to 1. If so, your only option might be to open your wallet and buy an 8.5GB dual-layer DVD with commercial LM or NT Rainbow Tables.

Like the other tools referred to in this article, Ophcrack is included in the Debian repositories. The Ophcrack utility requires rainbow tables and the hashes from the Windows machine. After completing the install, the investigator can work conveniently with the GUI and just double-click to decipher a user's password (Figure 5).

Domain Controllers

A different approach is required for Windows systems that log in to domain controllers; in this case, the credentials are not stored locally on the client. However, in many cases it is sufficient to run a network sniffer to capture the login exchange, identify the relevant data packets, save them to a file, and then feed a dump to Ophcrack. Of course, this is more complex, and you do need live access to the network.

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