Valve has added a CAPTCHA confirmation to the Steam trading process.

The additional step was added as a measure against malware making unwanted trades on an account holder's behalf.

"We’re updating trading to include a captcha as part of confirmation process. This is to prevent malware on users’ machines making trades on their behalf.," said Valve's John Cook.

"We know it’s a bit of a hassle, and we don’t like making trading harder for users, but we do expect it to significantly help customers who are tricked into downloading and running malware from losing their items."