There is a rogue .scr file floating around steam. Generally in the chat boxes. generally the link starts with myscreen.net, which is a tinyurl link, which auto-downloads the rogue file to your computer. The file is designed to corrupt your steam, and hijack your passwords. Here is the malwarebytes blog about it, for more info. https://blog.malwarebytes.org/fraud-scam/2014/11/rogue-scr-file-links-circulating-in-steam-chat/ SERIOUSLY, if you suspect anything, NEVER click on a link, until you ask what it is first.