Data routinely gathered in Web logs, such as Internet Protocol (IP) address, cookies, operating systems, browser type, and user-agent strings can threaten online privacy because they can be used to identify the activity of individual machines, according to Microsoft researchers. However, they say an analysis of such data when anonymized can help detect malicious activity and improve overall Internet security. The researchers found that HTTP user-agent information can accurately tag a host with an accuracy of 92.8 percent when more than one user ID was linked to a single host, such as with a family that shares a single computer. The researchers also found that even anonymized data can leak information. "[C]oarse-grained IP prefixes achieve similar host-tracking accuracy to that of precise IP address information when they are combined with hashed [user-agent] strings," the researchers say. They aimed to determine how much identifying information gets revealed by common identifiers and to understand the patterns of aggregated activities and explore their implications. "Our analysis suggests that users who do not wish to be tracked should do much more than clear cookies," the researchers note.

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