ASCOMP LeakCheck is a Windows utility that checks passwords and email addresses against known data breaches. ASCOMP Software GmbH offers a free Standard edition for personal use and evaluation, alongside a paid Professional edition.
Filling the password list
LeakCheck accepts manually entered passwords and imports from CSV files. Manual entry pairs each password with an optional source, such as a website or service name. After adding entries, you apply the list and choose which passwords to activate for checking.
Remove selected and Remove all controls clear entries from the list, while Hide passwords conceals their displayed values.
Browser import supports Chrome, Edge and Firefox through a CSV export workflow:
- Choose the relevant browser’s import command in LeakCheck.
- Export passwords from that browser and save the CSV file.
- Return to LeakCheck, choose Import CSV, and select the saved file.
Comparing passwords with known leaks
Selecting Check now checks the activated passwords against Have I Been Pwned. LeakCheck uses k-anonymity for this comparison: it sends an anonymized fragment of a password hash rather than the password itself. The password list displays a leak count beside each entry and retains its source information. Password checks have no request limit.
Email breach records
LeakCheck keeps email addresses in a separate list, with an Add screen for entering addresses manually. You activate the addresses to check, then select Check now. LeakCheck sends the addresses to Have I Been Pwned over HTTPS and evaluates the response. For an affected address, the results identify relevant breaches by name, title and date.
Each address consumes a separate request, and both editions enforce per-minute and daily limits. If a limit blocks further checks, the next checking window must open before those requests can proceed.
Status and local storage
LeakCheck’s dashboard separates password and email results. It shows counts of secure entries, leaked entries, detected leaks and failed checks for each group. Only activated passwords and email addresses contribute to its security calculation. The dashboard also records the most recent automatic check.
LeakCheck saves its password and email lists on the local PC. Windows Data Protection API encrypts that data with a key specific to the Windows user account.
Scheduled monitoring
Professional users can monitor passwords and email addresses automatically. LeakCheck provides separate switches for the two lists, then lets users choose weekdays and a checking time. Start and Stop controls govern the schedule, and the monitor checks the entries that users have activated. When a check finds a new breach, LeakCheck opens and notifies the user.
Professional also permits commercial use, while Standard covers personal use and evaluation.
