– Some hackers are exploiting Microsoft’s offer of free upgrades to its new Windows 10 operating system.

Security researchers are warning about a wave of bogus spam e-mails with malicious attachments, labeled as if they’re legitimate copies of the new program.

The attachments contain a “ransomware” program that, when opened, locks all the data on a computer and demands payment to release them.

Researchers at Cisco Systems say the e-mails are designed to look like an official upgrade notice from Microsoft Corp., but several words have random, out-of-place letters and punctuation.

Another important clue: Microsoft says its update mechanism provides computer owners with a notice on their screens — not via e-mail — when a direct Internet download is available. Experts warn against clicking on files that come with unsolicited e-mails.

ASSOCIATED PRESS