Steam will now check that you're a legitimate, human user and not a bot with a CAPTCHA test.

You've probably seen CAPTCHA tests at countless of secure websites. The test simply presents the user with a slightly obscured series of numbers and letters, and ask him or her to type them in, something a human can do easily, but not a bot, which can be programmed to perform the same action again and again otherwise.

In Steam's case, the new CAPTCHA test is aimed to protect users from Malware that takes over their account and empties out their inventory. GameSpot reported on such an issue back in September, when a Java program took over users' Steam accounts after they clicked a link in Twitch chat. Users can lose not only Steam Trading Cards, and in-game Team Fortress 2 and Counter-Strike: Global Offensive that way, but also actual games and coupons.

"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," Valve's John Cook said in the Steam Trading Cards Group discussion. "We’ve excluded a few of the existing third-party trading services from this requirement so they can continue to function."

Valve has been making several changes to the way Steam trading works recently. In November, it added a 30-day waiting period before users can trade gifts, and in December, it changed its policy to stop users from gifting games bought for cheap in one country to users in another country.