PyPI Bans Inbox.ru After Massive Spam Campaign and 1,500+ Fake Project Uploads

The Python Package Index (PyPI) has banned new account registrations and email additions from the inbox.ru domain, following what is now confirmed as a large-scale spam campaign that unfolded in June and July 2025.

“A recent spam campaign against PyPI has prompted an administrative action, preventing using the inbox.ru email domain,” wrote Mike Fiedler, PyPI Admin and Safety & Security Engineer at the Python Software Foundation (PSF).

Between June 9 and July 11, 2025, attackers created over 250 user accounts, publishing 1,525 fake projects. While these projects contained no malicious code, they exploited a loophole in PyPI’s structure—using misleading entry points to mimic legitimate command-line interfaces of popular packages.

“The campaign created over 250 new user accounts, publishing over 1,500 new projects on PyPI, leading to end-user confusion, abuse of resources, and potential security issues,” Fiedler explained.

This attack wasn’t about malware delivery—at least not yet. The attackers seemed focused on name confusion and package impersonation. They employed a deceptive tactic called slopsquatting, where packages mimic the names of legitimate libraries or their entry points, misleading users—especially when assisted by third-party recommendations or AI tools.

“This wasn’t a case of malware, but possibly using popular projects’ entrypoints… This may have proven to be a ‘dry run’ for a future attack,” Fiedler noted.

The campaign came to light after a user reported that Sonnet 4, a large language model, recommended installing a nonexistent PyPI project—a textbook example of slopsquatting.

“This is a good reminder that users should always verify the project names they are installing, and not copy & paste the name of a project suggested by a third party, such as an AI model or random person on the internet,” Fiedler emphasized.

Related Posts:

• Project Quarantine: PyPI’s New Line of Defense Against Malware
• PyPI Swiftly Patches Privilege Escalation Flaw in Organizations Feature
• PyPI Poisoned: 116 Malicious Packages Target Windows and Linux
• Cybercriminals Increasingly Target Google, Microsoft, and Amazon in Sophisticated Phishing Schemes
• Malicious PyPI Package Targets Discord Developers with Token Theft and Backdoor Exploit