Classi4u

We've been tracking a persistent trend of credential stuffing attacks targeting smaller, regional platforms, often leveraging older breach data. What really struck us with the recent Classi4u breach wasn't the volume of records—a relatively modest 204,511—but the age of the breach itself. The fact that credentials from a 2017 incident are still circulating and potentially being used successfully highlights the long tail of risk associated with older data leaks and inadequate password security practices. The data had been circulating quietly, but we noticed increased chatter on several dark web forums suggesting it was being actively used in ongoing attacks.

Classi4u's 2017 Breach: Still a Threat

The Classi4u breach, which occurred in December 2017, exposed 204,511 user records from the US-based classified ads platform. The data included email addresses and Base64-encrypted passwords. This breach caught our attention because of the age of the data and observed discussions indicating that the exposed credentials are still being actively traded and used in credential stuffing attacks. The persistence of this data in the threat landscape underscores the importance of proactive password resets and the limitations of weak encryption methods like Base64 for password storage.

Key point: Total records exposed: 204,511

Key point: Types of data included: Email addresses, password hashes (Base64-encrypted)

Key point: Sensitive content types: User credentials

Key point: Source structure: Not specified, likely a database export

Key point: Leak location(s): Dark web forums, combolists

Key point: Date of first appearance: 04-Dec-2017

The Classi4u breach serves as a stark reminder of the enduring risk posed by older data leaks. While the use of Base64 encryption might have seemed adequate at the time, it's now easily reversible and offers virtually no protection against modern cracking techniques. This highlights the critical need for organizations to implement robust password hashing algorithms (like bcrypt or Argon2) and regularly update their security practices to stay ahead of evolving threats.

External Context & Supporting Evidence

While the Classi4u breach itself didn't garner widespread media attention at the time, similar breaches involving older data have been highlighted by security researchers. For instance, Troy Hunt, creator of Have I Been Pwned?, frequently discusses the risks associated with "combolists" containing credentials from various breaches, emphasizing their use in credential stuffing attacks. The fact that Classi4u credentials are now appearing in these combolists demonstrates the platform's exposure to this wider threat landscape. One Telegram post claimed the files were "freshly cracked from a recent combolist update", which suggests the data is still being actively processed and distributed.

Email · Address · Password · Hash