Microsoft Outlook PST Hash

What is Microsoft Outlook PST?

The **Microsoft Outlook Personal Storage Table (PST) format** is not a cryptographic hash algorithm but rather a proprietary binary database structure designed to store email messages, contacts, calendars, and other Outlook data. Introduced in the late 1990s as part of Microsoft’s Outlook suite, the PST format evolved from earlier proprietary formats like the **DBX** (used in Outlook Express) and was optimized for hierarchical storage of Outlook items. Structurally, a PST file is a **hierarchical, self-describing database** built atop a **tagged binary format**, where each record (e.g., emails, attachments) is stored as a **tagged-length-encoded (TLE) structure**, with metadata headers (e.g., `PR_*` properties) and payloads. The format lacks native encryption by default, relying on external mechanisms like **S/MIME or BitLocker** for security, though older versions (pre-2003) stored passwords in reversible hashes (e.g., **MD4-based hashes** for legacy authentication). Its primary use-case was local email archival and synchronization with Microsoft Exchange, though its lack of standardization and proprietary nature led to vulnerabilities and compatibility issues.

The PST format is **inherently vulnerable to cracking** due to its reliance on weak or absent cryptographic protections in older versions. Historically, **unencrypted PST files (pre-2003)** stored passwords as **MD4 hashes without salting**, making them susceptible to **rainbow table attacks** or brute-force cracking, especially since MD4 is known to be vulnerable to collision attacks and lacks collision resistance. Even newer versions (post-2003) introduced **AES encryption (via EDB format)**, but the PST container itself remains vulnerable to **forensic extraction** due to its **predictable structure and lack of integrity checks**. Additionally, the format’s **hierarchical tagging system** allows attackers to **reconstruct metadata and payloads** without full decryption, while **GPU-accelerated tools** (e.g., **Hashcat** or **John the Ripper**) can efficiently crack legacy password hashes. Furthermore, the **absence of HMAC or digital signatures** in PST headers enables **malicious tampering**, and **side-channel attacks** (e.g., timing analysis) can exploit poorly implemented encryption in older Outlook versions. Modern exploits often leverage **PST parsing libraries** (e.g., **libpst**) to dump plaintext data from corrupted or unencrypted files, rendering the format a prime target for **data recovery and forensic analysis**.

Identifying Microsoft Outlook PST Hashes

Identifying a hash blindly is often difficult because multiple algorithms can output strings of the exact same length. For example, a standard 32-character hexadecimal string could be MD5, NTLM, MD4, or LM. To definitively identify Microsoft Outlook PST, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack Microsoft Outlook PST

If you need to recover the plaintext password for a Microsoft Outlook PST hash during a penetration test or forensics investigation, you must supply the correct module ID to your cracking software. Use the exact commands provided at the top of this page to target the hash successfully.