Mozilla permanently shut down its Firefox Send service for transferring files after people used it to launch online attacks, the nonprofit announced Thursday.

"Firefox Send was a promising tool for encrypted file sharing," Mozilla said in a statement. "Unfortunately, some abusive users were beginning to use Send to ship malware and conduct spear phishing attacks." Spear phishing is a personalized attack designed to fool you into sharing sensitive information like passwords.

Mozilla paused the Send service during the summer when it detected the problem, then decided it's not worth the expense of relaunching.

Mozilla just laid off a quarter of its 1,000 employees to try to cope with shrinking revenue from search-engine partners like Google during the coronavirus pandemic. The nonprofit is trying to expand into new areas, but the Firefox Send service's fate shows it's not easy to branch out beyond its core product, the Firefox web browser.

Two key services that Mozilla will continue to push are designed to improve your online privacy: its $5 per month virtual private network, or VPN, and its simpler $3 per month Firefox Private Network.

Also canceled is the Firefox Notes service, which let people synchronize notes across multiple devices. The Notes app for Android will be removed in November, and although the browser extension will remain longer, Mozilla won't develop it beyond adding an option to export notes.