An individual with the handle “Roddds” found the credentials on Friday after investigating a phishing message they received.
“Earlier today, I received one of those run-of-the-mill phishing emails,” Roddds wrote in a Reddit post on Friday. “I opened the URL that the email wanted me to open, but leaving out the .php file in the end.”
The user was directed to a server, which among other files, hosted a text file containing 47,130 email and password pairs for Hotmail and MSN. They then wrote a script to test whether the accounts were valid. After running the script for two hours, 85 percent of the credentials turned out to be accurate.
Roddds notified Microsoft, which owns MSN and Hotmail, about the issue. The server hosting the file was subsequently taken down.
“Guys at Microsoft were extremely nice, and it also felt like I had actually done something,” Roddds wrote.
Upon being notified of the issue, Microsoft immediately marked all affected accounts as compromised and has contacted all account owners to help them regain access, a company spokesperson told SCMagazineUS.com in a statement Tuesday.