• by Wendy Davis  @wendyndavis, September 10, 2008

Privacy advocates had mixed reactions to Google's recent announcement that it will move to anonymize search logs after nine months.

The company previously stored users' IP addresses coupled with their search queries for 18 months, so advocates say that nine months is a step in the right direction. At the same time, some are questioning why Google is keeping the data for even that long.

"The combination of pressure from regulators and competition is helping privacy in search," said Ari Schwartz, vice president and chief operating officer of the digital rights group Center for Democracy & Technology. But, he said, it's open to debate whether Google requires IP logs for nine months.

Jeff Chester, founder and executive director of the Center for Digital Democracy, added that it was not immediately apparent why Google needed to store information about search users for months. "They should be able to get rid of that search data right away," he said.

European regulators earlier this year said that search engines should discard records of IP addresses as soon as possible, and proposed an outside limit of six months. This week, Google sent the EU a 20-page document explaining why it wanted to retain that information for nine months.

The company said it used information about search activity to improve results and prevent fraud. "Log data is essential to prevent and investigate threats to our users," the company wrote to the EU.

Google also argued against slicing the time to shorter than nine months. "As the period prior to anonymization gets shorter, the added privacy benefits are less significant and the utility lost from the data grows," the company wrote in its blog.

But Schwartz, for one, questioned why that should be the case. "Eventually we will end up at a place where the engineers are getting what they really need to prevent fraud and improve products rather than all the data they could possibly have for any purpose, but it doesn't seem that we are quite there yet."

There are further questions about how Google will anonymize the data. Previously, Google said that anonymization would involve deleting the last two digits of an IP address. But that method does not completely protect people's identities, because there is a lot of identifying information in the remaining portion of the IP address.

And in some cases, users' identities can be determined just by examining a record of all search activity originating from their computers, even without knowing the IP address.

Until recently, Google kept search data indefinitely. The company only agreed to limit the time to 18 months when European regulators raised questions about the planned merger with DoubleClick. Google is currently facing a possible antitrust hurdle to plans to serve paid search ads on Yahoo sites.

Microsoft currently keeps search logs for 18 months, while Yahoo keeps them for 13 months.