If you use Gmail, AOL, Hotmail, MSN, Live.com or Yahoo for email, change your password immediately. Yahoo, Inc. was the latest web company to be comprised in recent weeks. It has been reported that more than 400,000 Yahoo, Inc. user names and password were stolen and published on the Internet. Although Yahoo has issued an apology for the security breach, many experts in the internet security field are criticizing Yahoo’s methods of protecting their users.

Cyber thieves were able to infiltrate Yahoo’s system and steal the information in just a day. Security experts believe that an Internet company, like Yahoo, should have better security measures in place to deter hackers.

“This points to some very lax security practices,” said Rob D’Ovidio, associate professor of criminal justice at Drexel University. “As an example, he noted that the hackers were able to produce more than 400,000 clear text passwords within a day. That indicates that Yahoo either did not encrypt them at all or used an encryption method that was easy to crack.”

So, what exactly happened? According to Yahoo spokesperson Dana Lengkeek, “an older file had been stolen from Yahoo Contributor Network, an Internet publishing service that Yahoo purchased about two years ago. It helps writers, photographers and videographers to sell their work over the Web.”

Lengkeek added, “We are fixing the vulnerability that led to the disclosure of this data, changing the passwords of the affected Yahoo! users and notifying the companies whose users’ accounts may have been compromised.”

This is just the latest dark cloud to hang over Yahoo. In the past year, the company has seen two CEO’s come and go and their results for second quarter were lackluster. But, Yahoo’s woes could be a thing of the past. Earlier this week, Yahoo announced the hiring of Marissa Mayer, formerly at Google, as their new CEO. At 37, she is the youngest CEO of a Fortune 500 company.