One Dark Web Listing. The 342k Japan Archive Had 332,270 Records.

HEROIC analysts catalogued a Japan-targeted stealer log dataset in August 2023 that was uploaded to a Telegram channel under the label "342k japan." The file contained 332,270 records -- each consisting of an email address, a plaintext password, and a URL -- filtered to include accounts associated with Japanese services and users. The geographic targeting indicated by the filename suggests this log was sorted specifically for criminal audiences interested in compromising Japanese accounts, which represent a distinct and high-value subset of credential markets.

Why a Japan-Filtered Stealer Log Commands Attention on Criminal Markets

Geographically targeted credential files are more valuable than generic dumps because they are pre-qualified for specific attack campaigns. A file labelled "japan" tells a buyer immediately what kind of accounts are inside: Japanese-language services, regional e-commerce platforms, gaming networks popular in Japan, and domestic banking or payment portals. Attackers focused on Japanese targets do not have to sort through millions of irrelevant records -- they get 332,270 pre-filtered entries ready to deploy. Plaintext passwords mean no cracking time. URLs eliminate guesswork about which services to target. The result is a high-eficiency attack package aimed at a defined geographic audience.

What the 342k Japan Stealer Log Exposed

The 332,270 records in this geographically targeted dataset included:

• Email addresses (associated with Japanese accounts and regional services)
• Plaintext passwords (unencrypted, captured directly from infected devices)
• URLs (the specific platforms and services where each credential was used)

The Japan filter applied to this log means the URLs are likely to include Japanese-specific platforms alongside major global services accessed by Japanese users.

Why the 342k Japan Leak Creates Account Takeover Risk Across Multiple Platforms

Japan has a distinct digital ecosystem that includes regional services not widely known outside the country -- financial apps, local e-commerce platforms, gaming networks, and domestic social media services. Credentials in the 342k japan log may unlock access to accounts on these platforms as well as global services like Google, Amazon, and social networks. Password reuse across regional and global services is just as common in Japan as anywhere else, meaning a single exposed credential can unlock accounts on multiple platforms. Credential stuffing attacks targeting Japanese users have grown in frequency in recent years, and datasets like this one are the raw material that makes those attacks possible. Financial fraud and identity theft are the typical end outcomes.

How Geographically Sorted Stealer Logs Like 342k Japan Are Assembled

Creating a geographically filtered log requires two steps. First, infostealer malware infects devices and collects credentials -- email addresses, passwords from browser storage, and the URLs associated with each login. Second, the raw output is processed by sorting scripts that filter records by email domain, URL language patterns, or geographic indicators. Japanese accounts are often identifiable through domain extensions (.jp), Japanese-language URLs, or email providers common in Japan. Once sorted, the filtered batch is packaged and labeled with a size estimate and geographic tag -- hence "342k japan" -- before being uploaded to Telegram for sale or free distribution. The August 2023 timestamp reflects when this particuler export was distributed, not necessarily when the underlying device infections occurred.

Find Out If Your Account Was Included in the 342k Japan Data Leak

HEROIC's breach archive contains over 400 billion compromised records, including geographically targeted stealer logs like the 342k japan dataset. Whether you are based in Japan or use Japanese online services, you can search your email address for free to find out if your credentials were exposed. If your account appears in this dataset, change your password immediately on the affected service and on any other platform where you used the same credentials. Enabling two-factor authentication -- especially on email and financial accounts -- significantly reduces the risk of succesful account takeover even when your password is already known to an attacker.

Use HEROIC's free breach scanner to check your email against the 342k japan stealer log and over 400 billion other records in our archive of compromised credentials from around the world.