Thursday, August 23, 2007

Pass the hash, NTLM style

Way back in 1997, a Windows exploit named "NT Pass the Hash" was posted on Bugtraq. This Unix-based tool was a modified SMB client that lets you use captured LanMan hashes, without having to decrypt them first.

After a mere ten years, someone has finally modernized this concept into a much more potent attack. Core Security has released Pass-The-Hash Toolkit, which runs on Windows and works with NTLM hashes. It's comprised of two key modules:
  • IAM.EXE - This tool "injects" another user's NTLM credentials into your current Windows logon session, given their username, Windows domain, and NTLM hash. You can then use the 'net' tools or any other Windows software that authenticates via NTLM, all under the assumed privileges of the compromised user account.
  • WHOSTHERE.EXE - Lists the usernames and NTLM hashes of all users logged on to a system.
No password cracking required! So if you own other systems on the network, you can just run whosthere.exe on them until you snag a domain admin's hashes. Or you could use a man-in-the middle attack, like the WPAD proxy exploit. As I discussed a few posts ago, the Metasploit guys covered several methods for grabbing NTLM hashes in their Tactical Exploitation presentation at BlackHat.

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