Yahoo plans to extend the amount of time it retains user search records to 18 months from 90 days. The company says it will consider keeping other types of information about its users for longer durations, too.

The new data retention policy marks an about-face for Yahoo. In late 2008, the company became the first big Internet search engine to commit to "anonymizing" a wide range of user data after 90 days in most cases. Such data — including records of Web searches, page views and ad clicks — are used to personalize Web content and target online advertising.

Yahoo anonymizes the data by stripping out portions of users' numeric Internet addresses, altering small tracking files known as "cookies" and deleting other potential personally identifiable information.

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